I’ve tried Safari, FireFox and Chrome, on Catalina, Mojave and BigSur, plus my iPad and iPhone.
Shift or Ctrl click countries clears others. Even using tick boxes on dropdown in iPad does work properly.
There is no way to change country lists or make new ones.
I’ve has to remove all products from all shipping that has OS countries in it… because I am unable to just remove a single country, or create a new list from scratch.
Can you please get this fixed?