This is an update about the Action Step.
Goto an Action Step, then "Set Variable Value", you can find "Math Formula Calculation" in Operation.
With this operation, you can now do formula calculation directly in the "Set Variable Value".
Math operations and function supported:
+, -, *, e, pi, PI, abs(), min(), max(), ceil(), floor(), log(), pow(), round(), sqrt(), sin(), cos(), tan()
*Please note that: if the formula is invalid, the system will return 0 to number variable and empty to text variable.