script in the new version

How to add a script in the new version ?

for example mail.com .
Insert button not found

   

Because Mozilla changed Firefox, X-Notifier 4.x doesn't have the ability to use custom scripts anymore. We can only choose from the menu in X-Notifier's "Options".
But for the time being, you can still use X-N 3.5.23, if you turn off automatic updates in FireFox: Tools, Addons, find X-Notifier, click 'More', scroll down to 'Automatic Updates', select 'Off' ...and you'll stay on the current version. If you want to reinstall 3.5.23, you can redownload it from https://addons.mozilla.org/en-us/firefox/addon/4490/versions

Is it possible to convert scripts into separate extentions? These extentions should be extremly simple, so conversion should be automated.

X-Notifier can check for such extentions and use additional functionality if present.