Apples SE doesn’t let you load a key, so you have to reencrypt your secrets for every Apple device you want them on… requiring hundreds of touches. The UX just sucks, which is why it’s not a thing.
To make a transaction several people around the world sign with hardware enclaves in their devices, or yubikeys/nitrokeys, and if the threshold of signatures is met, the enclave can permit bulk usage of key material that would not be safe to directly use locally.
The same enclaves that protect multi-billion dollar signing keys, can also be used to assist with secure policy-gated bulk transfer of passwords between the TPMs of different computers, among many other uses.
https://whitepaper.turnkey.com/