Heres a new idea: if we have the unified episodes screen (2. Inbox & Episodes by ueen · Pull Request #5192 · AntennaPod/AntennaPod · GitHub), we could bring back tabs (without viewpager=swiping - in order to keep the SwipeActions) and add a filter to the tabs that represent the “classical folders” (even though I would think of it more as categories), that could be a single field in the database, I think that should be optional (so that the tabs are hidden is there are no folders), the folder setting then could be added to the settings page of each podcast.
This should be rather simple to implement (once unified episodes are done)
What do you think, is that the functionality you are looking for? (Different, sorted Episodes lists)
Maybe this would also solve this usecase: Organising new podcast epsiodes?