After installing MAST a lot of Unity UI got glitched, I haven't tried many of the windows or tools to see how they're working, but the inspector and the shader graph are affected (I'll tell if I see something else). I'm using Unity 2019.4.16f1.
I know you're a busy guy as you work a lot, let me know if you need help with anything, I would love to help as MAST helps me a lot to develop my game. :P
Inspectors don't have scrollers (the side bar) anymore and components are fighting for space. I removed MAST and everything came back to normal.
[Update] I removed MAST from the project folder and created the shader I needed, after I've finished, I moved MAST back to my project, the glitch doesn't seem to appear now, but I won't delete the post because may help you to discover something? hm