You can now easily update user attributes via the new Set user attribute action. This action can be added to buttons, triggers, checklist tasks etc.
One common use case is to mark a checklist task as completed either when a related flow is completed or if the user explicitly opts out via a click on a button with a Set user attribute action. You could also use it to control the auto-start condition, e.g. only restart later if a specific button wasn’t clicked, by having the button setting an attribute used in the auto-start condition.
The action can also increment/decrement number attributes, in case you’re keeping a counter of something.