There are cases when you don't want to use app state management to control UI state. E.g. the entire app doesn't need to be aware of changing the state of a tab. In such a case, you can use a UI signal which is a local state scoped to a slot or reusable slot. In practice it means you will assign uiSignals.somethingActive = 'someId', typically on a DOM event and read it either in an extended tag or conditional. UI signals are powered by SolidJS and give you an elegant, granular way of making your HTML reactive. Use them responsibly and follow this simple rule; If multiple slots need to react to the same data change, you'd rather use app state management.