Where are SPD made Custom Actions ribbon buttons stored in xml files?

I would like to have ribbon button that call the workflow, but also have some custom JS in EnabledScript property.

Best would be to just copy-paste button definition can can be made with SPD, and just editing that single line, and the deploying it as .wsp solution.

But where are stored modifications for Custom Actions tied to specific list, specific form (its dispform for me)?