Chaining variables

I would love if we could be able to define variables by referencing other variables. So for instance for numbers, (Var 3) = (Var 1) + (Var 2). An example use case would be creating a counter badge on a checkout icon that increases as different a user adds products to the cart from an array of cards. You can set variables in this way with an interaction in a prototype but it’s really time consuming having to add and maintain Set Variable interactions across several buttons.