Well, this exact use case is mentioned on the pass website [0].

> One approach is to use the multi-line functionality of pass (--multiline or -m in insert), and store the password itself on the first line of the file, and the additional information on subsequent lines.

The Android Password Store app [1] also handles this format, interpreting the first line as the password and displaying the subsequent lines as additional information.

[0] https://www.passwordstore.org/

[1] https://github.com/android-password-store/Android-Password-S...