Hi there,
I haven’t tested it myself, but before applying damage, perhaps you want to get your damage class with custom variables, create object from class, modify variables values based on current ability, then get class and connect it to apply damage. On the other side, event any damage, get damage class, create object from class and get your custom variables to proceed with the rest of your damage calculation workflow.
Again, not sure if that works. Perhaps the solution with interface communication from the previous post should do the trick much easier.
You may want to try creating a data table for every damage type with all parameters associated based off a struct variable. On the target side, event any damage, get damage type and read a data table to extract queried variables.