If you would like to use incompatibilities on your manual planning process here are a few tips that might be helpful.
First, the IMG settings:
Assign the methods to a strategy
The method VSRI_CHECK triggers a warning message if a incompatibility is violated; the VSRI_CHKRJ triggers an error message if a incompatibility is violated. I would assign both methods to the strategy, then your incompatibility settings would define the system behavior.
Here you have your manual planning settings
Here you define that the incompatibility must not be violated
And that is the system behavior on the transportation cockpit, when the incompatibility is violated: