Since July (2023.7.0 release), Bitwarden does allow TOTP codes to be auto-filled. Thus, I will close this thread as completed.
However, please note that in the current implementation, Bitwarden only has 18 keywords used to identify TOTP input fields, and unfortunately, there is not yet an option to use custom fields that are linked to the TOTP autofill function. Anybody who is interested in persuading Bitwarden to make improvements to the TOTP autofill functionality can start a new Feature Request topic.