who like to store anything online??? That's most of the stupienst things you can ever do if money is involved.

powerplant likes to use coinomi offline. and that is no problem at all.
i think (need to look at the sourcecode) the wallets core is by design offline but connected with additional online services.

but seed and key-creation is an offline process with no external server messaging.

that was the question. but you are right: online wallets should not be used. never ever. you give your private keys in someons hands. and no server is unhackable.