It is already there. Click the tab for System Quick Key Status, then right click. You will see Set All On and Set All Off. Make sure that when you Read from Scanner or Write to Scanner that the QKs are set for the way you want them. Sometimes the QKs seem to be on by default when you add channels from the database into your FLs, and you have to make sure they are off if that is what you want.
Sometimes when I Write to Scanner, the QKs for all systems seem to be on, then for example, in my Favorite List for LA County Conventional (Fav QK 1), all the System QKs (about 30 of them) are turned on. Shutting each off is a PITA within the scanner
By the way, in each of your Favorite Lists, you will Department Quick Key Status for each system. You can also do the same thing, Right Click and turn all of or on.