Will the seed phrase (12 words) from a version 3.x wallet successfully create the private keys with Electrum V4.x ?
It's been a while since I upgraded to v4 but I think it recognised my wallet files too?
It's also possible to use a master private key on many different pieces of bip39 compliant wallet software and tools from your electrum wallet. That's the part that has quite good cross compatibility afaik.