A FIDO implementation that is unlocked with a passphrase. Now use the TextBlade as a hardware key.
A separate passphrase unlocks a password manager, which might be part of the app, or perhaps a separate (extra cost) capability. This came under some fire elsewhere as the things I was suggesting were considered too easy to hack. But I'll mention them here as I'm delighted to expose my ignorance to a larger group in the hope that someone smarter than me might see a way forward to solve the greater problem.
Essentially, I'd like to have the TextBlade save and enter passwords, using the app as a password manager. The physical TextBlade is 'something I have', the passphrase is 'something I know' and perhaps (perhaps!) some associated biometric like my typing rhythm and finger placement is 'something I am'. That last is pretty tricky given how difficult it is sometimes just to type the right character. Especially in an obfuscated password entry field.
How that gets done securely, how it's backed up and preserved, well that's not my specialty.