You create an auto command button…
Read what i wrote above. If you look at the tutorial also. You can see one column says auto command and in it a name of auto command button
But instead of mapping to nav screen. Dont put any mapping at all. Remove mapping and save it.
Then in the rule you can find the name of button.
After rule is created… you create that custom button from menu settings and put name of button you made and save.