Hmm. Who does not backup their wallets on the initial setup?? I already have a seed and do not wish it to share anywhere else on the internet, especially other apps. So I had some bitcoin in mycellium (call it portion 1), then had transfered another batch of bitcoin to same wallet (call it portion 2), for which BCH was already claimed. How do I claim BCH for portion 1 of bitcoin in my mycellium wallet without sharing seed, nor bitcoin leaving mycelium app and staying maximally safe?

That would be helpful, lol.