Are you referring to:
- autofill on shortcut / extension click, or
- the
Autofill on Page Load
option
For the former, others have already commented on how it is copied into clipboard.
For the latter, there is an existing feature request for auto-copy behavior (✅ Also copy TOTP code after autofill) and someone already has an implementation in the review process: TOTP Copy on Autofill
Whether there should be a new keyboard shortcut can be a separate question to discuss though.