manage a hidden template instead since this will come handy when dealing with multiple selection

app/javascript/controllers/combobox_controller.js

@@ -1,7 +1,9 @@
 import { Controller } from "@hotwired/stimulus"
 
 export default class extends Controller {
-  static targets = [ "label", "item", "hiddenField" ]
+  #hiddenField
+
+  static targets = [ "label", "item", "hiddenFieldTemplate" ]
   static values = {
     selectPropertyName: { type: String, default: "aria-checked" },
     defaultValue: String
@@ -30,7 +32,7 @@ export default class extends Controller {
     this.#clearSelection()
     item.setAttribute(this.selectPropertyNameValue, "true")
     this.labelTarget.textContent = this.#selectedLabel
-    this.hiddenFieldTarget.value = item.dataset.comboboxValue
+    this.hiddenField.value = item.dataset.comboboxValue
   }
 
   #clearSelection() {
@@ -38,4 +40,17 @@ export default class extends Controller {
       target.setAttribute(this.selectPropertyNameValue, "false")
     })
   }
+
+  get hiddenField() {
+    if (!this.#hiddenField) {
+      this.#hiddenField = this.#buildHiddenField()
+    }
+    return this.#hiddenField
+  }
+
+  #buildHiddenField() {
+    const [field] = this.hiddenFieldTemplateTarget.content.cloneNode(true).children
+    this.element.appendChild(field)
+    return field
+  }
 }

app/views/filters/settings/_controls.html.erb

@@ -3,7 +3,7 @@
   <%= hidden_field_tag :expand_all, true, disabled: !user_filtering.expanded?, data: { toggle_enable_target: "element" } %>
   <%= render "filters/settings/sorted_by", user_filtering: user_filtering %>
   <%= render "filters/settings/indexed_by", user_filtering: user_filtering %>
-<%#= render "filters/settings/tags", user_filtering: user_filtering %>
+  <%#= render "filters/settings/tags", user_filtering: user_filtering %>
 <%#= render "filters/settings/assignees", user_filtering: user_filtering %>
 <%#= render "filters/settings/creators", user_filtering: user_filtering %>
 <%#= render "filters/settings/closers", user_filtering: user_filtering %>

app/views/filters/settings/_indexed_by.html.erb

@@ -7,7 +7,9 @@
       </span>
     </button>
 
-    <%= hidden_field_tag :indexed_by, nil, data: { combobox_target: "hiddenField", filter_settings_target: "field" } %>
+    <template data-combobox-target="hiddenFieldTemplate">
+      <%= hidden_field_tag :indexed_by, nil, data: { filter_settings_target: "field" } %>
+    </template>
 
     <%= filter_dialog "Filter by…" do %>
       <strong class="popup__title">Filter by…</strong>

app/views/filters/settings/_sorted_by.html.erb

@@ -12,7 +12,9 @@
       </span>
     </button>
 
-    <%= hidden_field_tag :sorted_by, nil, data: { combobox_target: "hiddenField", filter_settings_target: "field" } %>
+    <template data-combobox-target="hiddenFieldTemplate">
+      <%= hidden_field_tag :sorted_by, nil, data: { filter_settings_target: "field" } %>
+    </template>
 
     <%= filter_dialog "Sort by…" do %>
       <strong class="popup__title">Sort by…</strong>