Optional Login steps, specifically TOTP

[Lockszmith-GH]

Anyone can give pointers on how to implement a flow with optional steps?

What I have now is the following:

• Username / Password -> TOTP
• Passwordless login with PassKey -> TOTP
• Plex social login

1st I'd like to make the TOTP optional, so it will have an option that's equivalent to - "don't ask me again on this device"
next I would like to add the above TOTP step after the Plex login.

Thanks in advance.