I noticed today on the Keyboard Maestro 10 end item a mention of the fact that I had not enabled KM for Screen recording in the system preferences.
I checked the system preferences and it is enabled there… Not sure if KM fails to see it, if the System is not properly sharing the status, etc…
You may need to add the Keyboard Maestro Engine, manually. Right click Keyboard Maestro in Applications > Show Package Contents > Contents > MacOS and drag Keyboard Maestro Engine into the Security screen you reference.