This is a simple bug in Construct2.
You can create an action that moves a sprite or a text to certain layer, but you can't to the same with a button. Buttons don't have 'move to layer'.
Steps to reproduce:
1-Add event > system > every tick (could be anything here)
2-Add action > select a button from your project > ??? there is no move to layer
If you do the same to a text object you have that option.
It is also missing the option to change z order(move to top and move to bottom) but I realize it may be not possible to do with a button. Maybe?