Note on Page with parameter - gmail notes

I would like to add a feature to make this plugin more useful for gmail. Gmail URLs als like this:
https://mail.google.com/mail/u/0/#SOME_THINGS/MAIL_ID
If I could make floatnotes to display a note only on
https://mail.google.com/mail/u/0/#.*/MAIL_ID
this would result in being able to attach a note to a mail (or a conversation).

Or something like: only on this website where parameter ends with MAIL_ID

The MAIL_ID is a String of numbers and letters without special symbols.