The Hot Key for "OK" button is always Enter key. For "Cancel" always Esc-key
I understand that completely, but then it doesn't make sense to underline them when that function is not working. Ergo: it's inconsequent.
For example, I've noticed that in the action "Create Variable" the "Alt+V" (to jump to the "variable value" field) is also not working. If that's on purpose (which I cannot imagine) then remove the underlined letter, just to prevent to give the user the idea/impression that it should work.