The Until action executes a list of actions until conditions are met. The Until action condition is not evaluated UNTIL the end of the Until Loop, so it will always execute all Actions in the Until block at least once.
Drag one or more actions into the No Action area.
Select a way to meet the conditions:
Add a new condition by clicking the green + button beside New Condition to select from a list of available conditions.
Conditions are grouped by category. See the Conditions section for further details.
After selecting a condition category you can make further choices. For example, if you choose the Application Condition you can choose a specific application to be running, or at the front, and so on.
Add further conditions by clicking the green + button again.
You can break out of the loop, retry this iteration, or skip to the next iteration with the actions:Redirect Control Flow actions.
See this Keyboard Maestro Forum post: About the "Until" action functioning