i have a really big problem. today I synced my Anki system and many complete decks vanished from the site. Weirdly I can reach those cards over “card management”. there I can see that they are still saved in those old decks – which don’t exist anymore. so how can I restore the decks without having to individually putting these cards into new decks?
Run Tools > Check Database. That usually is enough to repair those connections, so the decks will show up again in the main Decks list.