Unchained Action Economy modifiers

My group uses Unchained Action Economy rather than the Standard/Move/Swift//Full system. All characters have three actions in the system with a weapon attack counting as one action. So a level 1 creature or character can have three attacks in a round if they don't need to move, with a cumulative -5 on the attack action on every attack after the first (so -5 on the second then -10 on the third). What I've found when DMing is its very slow to do iterative attacks with creatures. I have to start the attack again, applying the -5 or -10 and carry on. There is the option to have multiple attacks on the Attacks tab but that will just roll those attacks if a Full Attack action is chosen and you can't modify how many attacks you have. I guess what I'm after is a selector box on the Attack dialogue to tick how many actions you're spending on attacks; so 2 actions it will roll two attacks, one at a -5 penalty. Tick three attacks and it will roll three attacks, one at a -5 penalty and one at a -10 penalty.