AppIndicator allowed your app to create menus in GNOME, like this:
python-appindicator, you could do it in Python. However, it looks like
python-appindicator is gone in the latest Linux distributions, including
Is there a replacement for it? I couldn't find much.
BTW I wish the the same library worked with different desktops, like KDE and GNOME, but
AppIndicator was GNOME-only, I believe.