I think having the ability to make your own trigger actions would greatly give freedom to map making and overall kinda like puzzles where you connect for example let's say you wanted to set variable 'A' to the id of object 'B' as an example or more and with that, you can connect perimeter 'A' action with perimeter 'B' essentially combine them together.
Would love to see something like this in PB2.5/3 perhaps. A really cool idea and an amazing feature perhaps allowing map making to make custom trigger actions and maybe perhaps coding in general and share customized trigger actions with others perhaps as well as combing different trigger actions together would greatly give freedom to map making and more complex mechanics.