Do you mean literally the actual sec keys for each address?
Having one key exposed won't allow deriving next pubs and secs right?
Discussion
I meant private keys and there is no "next keys". there is only used addresses and unused addresses in the wallet. unused ones aren't even known to the blockchain until they're being used so they do not matter.
Keys can be created offline. So they aren't known to the chain until they're being used hence I have no use for seeds to restor entire wallets if only 1-2 addresses are being used. Much more convenient to just import private keys to ANY wallet, do what I need to do and then just delete them again.