Is there any concept of private key rotation or something else? In case a client with a nostr key on it got compromised or something similar? With a traditional password passed logins I would just set a new password from another machine. Regeneration of a new nostr key would mean it's a new account isn't it?

There is Frost Key Rotation and/or Key bunkers

https://asknostr.site/question/note1534t79a5nk8ajcx8xqlsa3pr...

But it's still early and not all clients support it.