How do I add the "E" prompt to a movable object after I aim my crosshair in it?

yes it look ok, inside event you don’t have to do anything its a simple event.

make sure your current interactions around array is empty at the beginning.

When there is something in the array on overlap it needs to check its distance and prioritize as CurrentPrioritizedInteraction

on event tick you can check current interaction name always to diagnose -debug what is wrongly setup.
Cause if scanner is correctly assigning a valid interaction and ui says cannot find it. You should first check the interaction is really valid and if its why ui says null.

as you can see current interaction on widget ui is assigned from the event

make sure its type correct as InteractionComponent