Cool!
Is there a tool to do this with an existing 12/24 seed? Or does it support that even?
In this first version you can select "Create new wallet" > "Multishares backup", then you have to select your backup schema n-of-m, and then instead of showing you 12/24 worlds it displays `m` sets of 33 words to backup. Then you will need `n` of those sets of 33 words to recover your wallet.
Technically, this is an implementation of the Satoshi Labs SLIP39: https://github.com/satoshilabs/slips/blob/master/slip-0039.md
Matechamically, I know you know but it is based on Lagrange polynomial interpolation.
Discussion
Currently there are tools, yes. I should google to find them but yes, you decode your bip39 seed and encode it back with slip39.
