Can I Display our support number on the desktop tray icon
In the menu, sure, I do. Did you look at the KB article?
You sure can! The System Tray section on your policies will allow you to add tray menu options. You can find out more about what you can add here: https://help.syncromsp.com/hc/en-us/articles/360039894933-Policies-with-Policy-Inheritance-#sysmenu