How to add a keyboard shortcut for Insert Equation for Word 2016?

I tried Word >> Tools >> Customize Keyboard >> EquationInsert, but I can't seem to modify the "Press new keyboard shortcut" box.

I also tried System Preferences >> Keyboard >> Shortcuts >> App Shortcuts, but adding "EquationInsert" or "Insert an equation" did not produce any responses.

Correct procedure but: Write simply the word "Equation" (thats the word you have to call)

Tip: If you aren't sure what the menu name is for a command, click Help in that app and search for what you want, which will then show you the exact menu name.

There is already a shortcut ^= defined, you can find it in the Insert menu.

PS: The location of = on the keyboard depends on the keyboard layout, so it may not work with all layouts.