I actually just figured it out. I’m surprised I ended up coming across this. I have another script that’s used for fading out on deactivation, but I ended up just switching everything over to accompany the Particle ID and the int32 input. Here are some screenshots of the Niagara Scratchpad.
And here is the interior of the Node when placed inside the Niagara system. It allows for a custom time duration for how long you want the fade in/out to be.
And finally, I plugged the output parameter, which is the time frame, into the curve index for the “Erode Dynamic Parameter”
And well, it works. I feel like its just black magic. The solution was just sitting under my nose, in another custom parameter I had already made.
The system spawns with a total of 10 particles, but only shows ones specified by the int32 input, which is exactly as I wanted it to do. And they also smoothly fade in and out.
EDIT : The final example is cut short because the GIF file size requirement is pretty small. You get the idea, I increase the parameter first by one, then by two and then two again.