I had a similar question in October, but the responses didn’t fully solve this, sadly!
I still use Overcast and add favourites to a special playlist manually using the menu described in that thread. I believe the reason this doesn’t work better is that technically your Overcast stars are not intended as favourites, but recommendations for Overcast’s recommender engine.
IIRC, Castro has a better favourites system—but no playlists! So you have to choose between the two features. I’d love a best-of-both-worlds app, too.
I just tested and like castro favorite system — i don’t use playlist so thats not an issue – I think i will use both for now and see how much energy I could devote towards going back through my back catlog and making manual overcast “favorite” play lists
one downside to get the skip silence and volume boost = castro subscription; kinda cool marco has these free and is active developer - will keep to see how the app can mature perhaps he could be working to adding more management features…