Using the online demo as an example, there is currently a self-service action named "Add/Remove Service from Favorites". In my head, the ability to make an action conditionally available (based on one of more properties of the selected entity) would allow "Add Favorite" as an action for services that were not yet a favorite for me - while "Remove Favorite" would only be available for services that were already my favorite (this same thought process could be applied to the existing actions "Unlock Service" and "Lock Service").

Similarly (and maybe more compelling), an action like "Deploy Service" might only be available once certain criteria are met (an extension of sorts to the concept of scorecarding). Again referencing the demo service catalog, I could also see additional actions based on a distinguishing property like "Language" - maybe in our environment Python is managed distinctly different from React, and as such only certain actions would make sense in each context.

(There is also this feature request which also feels related...but not entirely overlapping.)