The file holding the QAT information frequently has problems. When SL can’t find it or can’t read it, it just creates a new copy of the default file.
Because of that, I make a backup copy of the file that controls those settings. In my case, it is found at C:\Users\[My user name]\AppData\Roaming\Articulate\Storyline\360\Workspace.xml. In a Mac environment, try a search with Finder to find the file.
When I close SL after making a change to one of those settings, I go there and make a copy of it. Then if I lose it, I copy the copy and rename that to the original name.
It doesn’t keeping you from losing the changes you make, but it does make it easier and quicker to restore them.