Keyboard Maestro cannot see various non-standard window-types, but that doesn't stop users from wanting to be able to test for them at times.
System Events can sometimes come to the rescue.
This macro lists every window visible to System Events by application.
Open the window you want to work with.
Run the macro.
It will take a few seconds to open the report in TextEdit.
Look for the related application.
See if the window you want to work with is listed.
If it IS listed then you have some options and can ask for help if you need it.
If it is NOT listed then unfortunately you're probably out of luck.
** Mission Control spaces are not comprehensively supported by AppleScript, so it's best to have only one space open when testing.
Window Discovery Tool → Windows System Events Can See v1.0.kmmacros (9.6 KB)