Bad new is: I think it's impossible to create a standard for this that's also compatible with SLIP39 standards without changing BIP39.
The main reason is it's nearly impossible to get the mnemonic back from the seed since it's a product of 2048 rounds of HMAC-SHA512 algorithm which is
Did you check website Slip39.com and their open source tools that is used for converting Bip39 to Slip 39:
https://slip39.com/https://github.com/pjkundert/python-slip39OneKey finally released support for SLIP-39 backup, but for now it's limited to their Pro variant
[v4.15.0]:
Source- BTW, I think it'd be better if the wallets that don't fully support it yet had a partial tag.Onekey ius basically Chinese Trezor clone with some modifications, so it's no surprise they added support for SLip39.
Anyway, this is a good thing, but I still prefer Trezor knowing short lifetime and support for Onekey devices.