That screenshot comes from a virtual device using this:
It is just a simple button that generates ‘pushed’ events (the ‘down_6x’ status is just used to initialise the button status without fearing setting off an automation). The Momentary capability calls the ‘push()’ method which sends the button pushed event.
I mostly use it as a momentary button with ActionTiles but the Momentary action works fine in the new app too.
*It doesn’t work in the Classic app because I deliberately left the ‘tiles()’ block out. *