How can we assign or remove a BADI to Appraisal Catalog?
You can add the enhancements(Badis) to the category in Phap_catalog under the "Enhancements" tab. Try to add all enhancements possible. Once you do this the appraisal templates under that category can utilize the enhancments.
In the Appraisal template, the enhancemtns are available in the tab "Layout" for layout specific enhancements and under the tab "Processing" tab.
In the Processing tab check for the button "Further template behaviour". All the other enhancments are added and removed here. Based on the filter value, the enhancement implementations can be added here.
Hope this helps you.