Ah, what is this about Garbage
Collector, though?
To put it it simply, it’s a system that removes objects from memory when they are no longer in use. It’s mostly fully automatic and you generally do not need to do anything about it; for example - when you call Destroy on the object. The memory it used to occupy will be (eventually) freed up.
More info:
https://wiki.unrealengine.com/Garbage_Collection_Overview
You were adding widgets and hiding them without referencing; when you created another new widget, the old one was already being eaten by the GC (best case scenario) since it had no valid reference. Technically, that’s a good thing! But you were unable to access the old widget anymore.