After uninstalling the GSConnect GNOME extension, its entry remains visible in Settings then Notifications under App Notifications. The toggle is present but non-functional (as the extension is gone). Attempts to remove it via dconf-editor (reset recursively on /org/gnome/desktop/notifications/application/org-gnome-shell-extensions-gsconnect/) and related commands do not clear the entry from the UI. The application-children key is empty (@as ), and no remnant extension folder exists.
I could reproduce this. It seems that the extension leaves some unwanted traces even when removed. Check with:
$ ls ~/.local/share/applications/org.gnome.Shell.Extensions.GSConnect*
/var/home/mike/.local/share/applications/org.gnome.Shell.Extensions.GSConnect.desktop /var/home/mike/.local/share/applications/org.gnome.Shell.Extensions.GSConnect.Preferences.desktop
You should be able to remove the unwanted entry in the App Notifications list by removing the leftover destop files: