I'm trying to set up some app-specific keystrokes (to remap that app's keyboard shortcuts to ones I prefer). If the keystroke is pressed and the if-else is not true, I want to pass the keystroke back to the operating system. Is this possible?
Example:
remap shift+command+[ if SigmaOS is running
If SigmaOS isn't running, perform whatever the default action is for shift+command+[ (eg. if Safari is running, change tabs)
Assuming "SigmaOS" is an Application? That's what Keyboard Maestro Groups can be used for - limiting Macros to certain Applications.
Just make a Group called "SigmaOS", keep your key-mapping Macros in that Group and set the Group to "Available in these applications" and using the + sign choose "SigmaOS" from the list of your Applications.
Here's how it would work for Macros that should only be active in GarageBand App for example: