@dodoistda Welcome to the forum!
I think the feature request that you had posted in (“Allow custom field names for TOTP autofill”) was essentially asking for the same thing that you are proposing, although the implementation details were left vague (linked fields had been mentioned only in cited a comment from a since closed feature request).
Regardless, I have now merged that thread (“Allow custom field names for TOTP autofill”) with a previously existing feature request topic (“Add TOTP as a Linked Field”) which was more explicit about using the linked fields feature for allowing the TOTP field name to be recognized as an autofill target. I have also modified the topic title to be more descriptive.
The thread you referenced is requesting access to variable names (e.g., $PASSWORD) that can be used to reference the username and password fields. That is beyond the scope of the current (merged) feature request.