diff --git a/src/modules/esl-toggleable/core/esl-toggleable.ts b/src/modules/esl-toggleable/core/esl-toggleable.ts
index 0b351353c..c2a4d9ba8 100644
--- a/src/modules/esl-toggleable/core/esl-toggleable.ts
+++ b/src/modules/esl-toggleable/core/esl-toggleable.ts
@@ -27,6 +27,9 @@ export interface ToggleableActionParams {
   activator?: HTMLElement;
   /** Event that initiates the action */
   event?: Event;
+
+  /** Custom user data */
+  [key: string]: any;
 }
 
 const activators: WeakMap<ESLToggleable, HTMLElement | undefined> = new WeakMap();