I’m no expert in the code (not even close), but I don’t think there is a standardized default action for buttons.
If you explore through the usermods, you may get some ideas on what has been done so far, but this is still WIP territory.
I’ve noticed the MoonModule fork has a rather in depth discussion of the code in various places.
Take a look through the MM KB to get some good examples of how things are structured.
Those with more intimate knowledge of the code may feel free to stomp over all my comments as they see fit…