Adding an email account to the new Google Workspace - ASAP

I have 2 Google Workspace accounts - New and Old.

The Old account [S] is on domain [F], in that it has additional domains one of them is [KM] where I have a specific email [K@KM].

The new account [N] is on domain [K] and I would like to have just the email [K@KM] there.

Unfortunately, when trying to do anything I end up having to first unlink the [K] domain from [S] and then link it to [N], but when doing an analogy test on another domain beforehand I still have to confirm that this email address, [K@KM], belongs to me, so I cannot unlink the domain from [S], because in [N] it will not verify the [K@KM] email there, which I can only handle from [S].