Feature Request: OtF to allow adding an item to the Effects Modifier

[Farmeroz]

Example provided from the GURPS Discord by SavageGM was "character casts Blur for a-5 to be hit and then on success of the spell the macro would automatically put a "-5 Blur" into the Effects Modifier.

If there's a way to do this via JS in the meantime, that would also be great.