Go Edit > Keyboard Shortcuts, from the Web Standard Set:

  1. Choose Miscellaneous
  2. Scroll to the Group As Mask command and select it
  3. Press combination of keys, I resolved on Alt + Shift + V
  4. Then click the + to add the key combination

Then OK to commit changes.

Using the same above process, assign a key combination for the Group as Mask cammand as well.