This can be achieved through a blueprint interface. In the BI you make bare bones functions, you simply tell it what the input and output variables are. Then in the Blueprint you are working on go to the blueprint properties and under ‘Interfaces’, go to ‘Implemented Interfaces’, click add and select you BI you made. The way this works is any time the function you made is called in one blueprint will also be called in all other blueprints. You can make so it is only called in that blueprint by itself, but that will still be called if another blueprint uses the function.
The way you implement it is to right click in your graph and add the function under ‘Interface Messages’. If you add it under ‘Call Function’ it will be the local version. From there you can either double click it on the graph or in the my blueprint section and put your implementation of the function in.
So for example you could have a witch cast a spell, and in the spell blueprint you call a function from a BI called SpellCastA, which could do something or remain empty, then have a flame blueprint that when it receives the message SpellCastA has been called the flames flair up.
You can find more information here: Blueprint Interface
Best Regards,
Ryan