Can't enter hotkey anymore

When I want to add a hot key trigger, no matter what i enter it will not show up.

This is undoubtedly due to some kind of security feature in Mojave, but I can't for the life of me find out where to enable this.

Any recommendations?

You may find this helpful:

If that does not resolve your issue, we will need more details from you.
Please read:
Tip: How Do I Get The Best Answer in the Shortest Time?

"Have you tried turning it off and on again?"

Never thought that would ever apply to a Mac. But such is life these days. Thanks very much for the suggestion, it resolved the issue for me.