I couldn’t get the node to work either. Perhaps it’s to be used for a different kind of emitter (note that the target is FXSystem Component, not Niagara Particle System). Anyhow, here’s a workaround I use:
In your Niagara System, create a variable that you will use to control the system with. I created a float that I will use to change the spawn probability from 1.0 to 0.0. After creating the variable, drag and drop it on the property you want to control it with:
Then add a blueprint node to control your particle system. Connect “Target” to your particle system and under “In Variable Name” put in “User.” and then the name of the variable you created in Niagara.
Hope this helps! Please up-vote and mark as answer if it’s what you’ve been looking for. Cheers!