Right approach to change materials of actors by widget

ok thanks, I set that. Things are really messed up right now. The close button of the post yoy answered ealier isn’t working any more.

I get a yellow ! explenation mark in the comiling of the widget. It’s a eventdispatcher I made earlier with the wrong name, but it still remains in the widget BP. I can’t delete it!
Nor do I see it at the Event Dispatchers list.

Is that maybe a problem? How can I delete this graph node?