diff --git a/.gitignore b/.gitignore
index edbcf679..b5aad5d0 100755
--- a/.gitignore
+++ b/.gitignore
@@ -7,6 +7,7 @@ docs/*
 !docs/*.ico
 .vscode
 .*.swp
+.DS_Store
 src/core/config/modules/*
 src/core/config/OperationConfig.json
 src/core/operations/index.mjs
diff --git a/src/core/operations/MultipleBombe.mjs b/src/core/operations/MultipleBombe.mjs
index dac7a334..a453ca34 100644
--- a/src/core/operations/MultipleBombe.mjs
+++ b/src/core/operations/MultipleBombe.mjs
@@ -60,95 +60,57 @@ class MultipleBombe extends Operation {
         this.args = [
             {
                 "name": "Standard Enigmas",
-                "type": "populateOption",
+                "type": "populateMultiOption",
                 "value": [
                     {
                         name: "German Service Enigma (First - 3 rotor)",
-                        value: rotorsFormat(ROTORS, 0, 5)
+                        value: [
+                            rotorsFormat(ROTORS, 0, 5),
+                            "",
+                            rotorsFormat(REFLECTORS, 0, 1)
+                        ]
                     },
                     {
                         name: "German Service Enigma (Second - 3 rotor)",
-                        value: rotorsFormat(ROTORS, 0, 8)
+                        value: [
+                            rotorsFormat(ROTORS, 0, 8),
+                            "",
+                            rotorsFormat(REFLECTORS, 0, 2)
+                        ]
                     },
                     {
                         name: "German Service Enigma (Third - 4 rotor)",
-                        value: rotorsFormat(ROTORS, 0, 8)
+                        value: [
+                            rotorsFormat(ROTORS, 0, 8),
+                            rotorsFormat(ROTORS_FOURTH, 1, 2),
+                            rotorsFormat(REFLECTORS, 2, 3)
+                        ]
                     },
                     {
                         name: "German Service Enigma (Fourth - 4 rotor)",
-                        value: rotorsFormat(ROTORS, 0, 8)
+                        value: [
+                            rotorsFormat(ROTORS, 0, 8),
+                            rotorsFormat(ROTORS_FOURTH, 1, 3),
+                            rotorsFormat(REFLECTORS, 2, 4)
+                        ]
                     },
                     {
                         name: "User defined",
-                        value: ""
+                        value: ["", "", ""]
                     },
                 ],
-                "target": 1
+                "target": [1, 2, 3]
             },
             {
                 name: "Main rotors",
                 type: "text",
                 value: ""
             },
-            {
-                "name": "Standard Enigmas",
-                "type": "populateOption",
-                "value": [
-                    {
-                        name: "German Service Enigma (First - 3 rotor)",
-                        value: ""
-                    },
-                    {
-                        name: "German Service Enigma (Second - 3 rotor)",
-                        value: ""
-                    },
-                    {
-                        name: "German Service Enigma (Third - 4 rotor)",
-                        value: rotorsFormat(ROTORS_FOURTH, 1, 2)
-                    },
-                    {
-                        name: "German Service Enigma (Fourth - 4 rotor)",
-                        value: rotorsFormat(ROTORS_FOURTH, 1, 3)
-                    },
-                    {
-                        name: "User defined",
-                        value: ""
-                    },
-                ],
-                "target": 3
-            },
             {
                 name: "4th rotor",
                 type: "text",
                 value: ""
             },
-            {
-                "name": "Standard Enigmas",
-                "type": "populateOption",
-                "value": [
-                    {
-                        name: "German Service Enigma (First - 3 rotor)",
-                        value: rotorsFormat(REFLECTORS, 0, 1)
-                    },
-                    {
-                        name: "German Service Enigma (Second - 3 rotor)",
-                        value: rotorsFormat(REFLECTORS, 0, 2)
-                    },
-                    {
-                        name: "German Service Enigma (Third - 4 rotor)",
-                        value: rotorsFormat(REFLECTORS, 2, 3)
-                    },
-                    {
-                        name: "German Service Enigma (Fourth - 4 rotor)",
-                        value: rotorsFormat(REFLECTORS, 2, 4)
-                    },
-                    {
-                        name: "User defined",
-                        value: ""
-                    },
-                ],
-                "target": 5
-            },
             {
                 name: "Reflectors",
                 type: "text",
@@ -217,11 +179,11 @@ class MultipleBombe extends Operation {
      */
     run(input, args) {
         const mainRotorsStr = args[1];
-        const fourthRotorsStr = args[3];
-        const reflectorsStr = args[5];
-        let crib = args[6];
-        const offset = args[7];
-        const check = args[8];
+        const fourthRotorsStr = args[2];
+        const reflectorsStr = args[3];
+        let crib = args[4];
+        const offset = args[5];
+        const check = args[6];
         const rotors = [];
         const fourthRotors = [];
         const reflectors = [];
diff --git a/src/web/HTMLIngredient.mjs b/src/web/HTMLIngredient.mjs
index bb01d7de..c7c024fb 100755
--- a/src/web/HTMLIngredient.mjs
+++ b/src/web/HTMLIngredient.mjs
@@ -39,7 +39,7 @@ class HTMLIngredient {
      */
     toHtml() {
         let html = "",
-            i, m;
+            i, m, eventFn;
 
         switch (this.type) {
             case "string":
@@ -142,10 +142,11 @@ class HTMLIngredient {
                 </div>`;
                 break;
             case "populateOption":
+            case "populateMultiOption":
                 html += `<div class="form-group">
                     <label for="${this.id}" class="bmd-label-floating">${this.name}</label>
                     <select
-                        class="form-control arg"
+                        class="form-control arg no-state-change populate-option"
                         id="${this.id}"
                         arg-name="${this.name}"
                         ${this.disabled ? "disabled" : ""}>`;
@@ -155,14 +156,20 @@ class HTMLIngredient {
                     } else if ((m = this.value[i].name.match(/\[\/([a-z0-9 -()^]+)\]/i))) {
                         html += "</optgroup>";
                     } else {
-                        html += `<option populate-value="${this.value[i].value}">${this.value[i].name}</option>`;
+                        const val = this.type === "populateMultiOption" ?
+                            JSON.stringify(this.value[i].value) :
+                            this.value[i].value;
+                        html += `<option populate-value='${val}'>${this.value[i].name}</option>`;
                     }
                 }
                 html += `</select>
                     ${this.hint ? "<span class='bmd-help'>" + this.hint + "</span>" : ""}
                 </div>`;
 
-                this.manager.addDynamicListener("#" + this.id, "change", this.populateOptionChange, this);
+                eventFn = this.type === "populateMultiOption" ?
+                    this.populateMultiOptionChange :
+                    this.populateOptionChange;
+                this.manager.addDynamicListener("#" + this.id, "change", eventFn, this);
                 break;
             case "editableOption":
                 html += `<div class="form-group input-group">
@@ -248,6 +255,9 @@ class HTMLIngredient {
      * @param {event} e
      */
     populateOptionChange(e) {
+        e.preventDefault();
+        e.stopPropagation();
+
         const el = e.target;
         const op = el.parentNode.parentNode;
         const target = op.querySelectorAll(".arg")[this.target];
@@ -260,6 +270,37 @@ class HTMLIngredient {
     }
 
 
+    /**
+     * Handler for populate multi option changes.
+     * Populates the relevant arguments with the specified values.
+     *
+     * @param {event} e
+     */
+    populateMultiOptionChange(e) {
+        e.preventDefault();
+        e.stopPropagation();
+
+        const el = e.target;
+        const op = el.parentNode.parentNode;
+        const args = op.querySelectorAll(".arg");
+        const targets = this.target.map(i => args[i]);
+        const vals = JSON.parse(el.childNodes[el.selectedIndex].getAttribute("populate-value"));
+        const evt = new Event("change");
+
+        for (let i = 0; i < targets.length; i++) {
+            targets[i].value = vals[i];
+        }
+
+        // Fire change event after all targets have been assigned
+        this.manager.recipe.ingChange();
+
+        // Send change event for each target once all have been assigned, to update the label placement.
+        for (const target of targets) {
+            target.dispatchEvent(evt);
+        }
+    }
+
+
     /**
      * Handler for editable option clicks.
      * Populates the input box with the selected value.
diff --git a/src/web/RecipeWaiter.mjs b/src/web/RecipeWaiter.mjs
index a8326b27..4c568c8b 100755
--- a/src/web/RecipeWaiter.mjs
+++ b/src/web/RecipeWaiter.mjs
@@ -205,6 +205,7 @@ class RecipeWaiter {
      * @fires Manager#statechange
      */
     ingChange(e) {
+        if (e && e.target && e.target.classList.contains("no-state-change")) return;
         window.dispatchEvent(this.manager.statechange);
     }
 
@@ -392,6 +393,15 @@ class RecipeWaiter {
         this.buildRecipeOperation(item);
         document.getElementById("rec-list").appendChild(item);
 
+        // Trigger populateOption events
+        const populateOptions = item.querySelectorAll(".populate-option");
+        const evt = new Event("change", {bubbles: true});
+        if (populateOptions.length) {
+            for (const el of populateOptions) {
+                el.dispatchEvent(evt);
+            }
+        }
+
         item.dispatchEvent(this.manager.operationadd);
         return item;
     }
diff --git a/tests/operations/tests/MultipleBombe.mjs b/tests/operations/tests/MultipleBombe.mjs
index f809859c..5c06ece4 100644
--- a/tests/operations/tests/MultipleBombe.mjs
+++ b/tests/operations/tests/MultipleBombe.mjs
@@ -16,9 +16,10 @@ TestRegister.addTests([
                 "op": "Multiple Bombe",
                 "args": [
                     // I, II and III
-                    "User defined", "EKMFLGDQVZNTOWYHXUSPAIBRCJ<R\nAJDKSIRUXBLHWTMCQGZNPYFVOE<F\nBDFHJLCPRTXVZNYEIWGAKMUSQO<W",
-                    "User defined", "",
-                    "User defined", "AY BR CU DH EQ FS GL IP JX KN MO TZ VW", // B
+                    "User defined",
+                    "EKMFLGDQVZNTOWYHXUSPAIBRCJ<R\nAJDKSIRUXBLHWTMCQGZNPYFVOE<F\nBDFHJLCPRTXVZNYEIWGAKMUSQO<W",
+                    "",
+                    "AY BR CU DH EQ FS GL IP JX KN MO TZ VW", // B
                     "THISISATESTMESSAGE", 0, false
                 ]
             }
@@ -35,9 +36,10 @@ TestRegister.addTests([
                 "op": "Multiple Bombe",
                 "args": [
                     // I, II and III
-                    "User defined", "EKMFLGDQVZNTOWYHXUSPAIBRCJ<R\nAJDKSIRUXBLHWTMCQGZNPYFVOE<F\nBDFHJLCPRTXVZNYEIWGAKMUSQO<W",
-                    "User defined", "LEYJVCNIXWPBQMDRTAKZGFUHOS", // Beta
-                    "User defined", "AE BN CK DQ FU GY HW IJ LO MP RX SZ TV", // B thin
+                    "User defined",
+                    "EKMFLGDQVZNTOWYHXUSPAIBRCJ<R\nAJDKSIRUXBLHWTMCQGZNPYFVOE<F\nBDFHJLCPRTXVZNYEIWGAKMUSQO<W",
+                    "LEYJVCNIXWPBQMDRTAKZGFUHOS", // Beta
+                    "AE BN CK DQ FU GY HW IJ LO MP RX SZ TV", // B thin
                     "THISISATESTMESSAGE", 0, false
                 ]
             }