I didn't see a native Keyboard Maestro way to click the OK button (which seems strange, I might just be overlooking something stupidly simple), but perhaps an AppleScript would work for you.
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# Author: Chris Thomerson
# Current Version: 1.0
# Version History:
# 1.0 (Initial script)
# Created: Thursday, November 18, 2021
# Modified: Thursday, November 18, 2021
# macOS: 11.6.1 (Big Sur)
#
# Notes:
# I claim no responsibility nor guarantee compatibility
# As with any kind of custom scripts, these must be tested thoroughly on each person's device
# May be used and distributed freely
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tell application "System Events"
tell application process "Keyboard Maestro Engine"
click button "OK" of window "Keyboard Maestro User Input"
end tell
end tell
You would place this AppleScript in the appropriate macro(s) that you want to click the button and in the appropriate spot.
HOWEVER, this working would be dependent on the name of the prompt button...if you change the button name in the prompt you would have to change it in the AppleScript as well.
It works for me in the whopping 3 minutes of testing I did on my local machine, but try it out on yours and let me know if it works or not.
Attached below is the script already in an action if you'd rather just import it and then drag it into your macros.
Roger, sounds good. Another option would to just simulate a keystroke, using Return as the keystroke. But the user prompt would have to be at the front and the appropriate button would have to be the default selection for that to work. So whether or not that would work would depend on how your macro is designed.