The idea is that you should configure the proper ruleset once for the login then you will be set forever. You can create rules in the global scope for things that will often need whitelisting. The top-left cell is the scope selector, from where you can access the global scope.

In any case, you can disable globally by selecting the global scope and toggle off matrix filtering, not recommended though, best is to create the needed rules so you do not have to ever disable globally.

If you submitted your specific issue in the forum I could probably guide you on how to solve your specific issue: https://discourse.mozilla.org/t/support-umatrix/5131