Spawn amount connected to slider

I have a simple rain system hooked up to an options menu that allow the user to change how heavy the rainfall is. The Particle system spawns the rain in sheets instead of constantly and the slider makes no difference to the rain amount except from turning it off at 0. How can I tie the value of the slider to the spawn parameter of the particle system?

I had to do something very similar before:

Instead of changing the Scale of the Spawn I want to change how many particles spawn. My current system looks like this but the slider doesn’t effect the rate of spawn.

I can confirm that Spawn/Rate can be controlled with a float param the same way as Spawn/RateScale can. (4.21) If it doesn’t work for you then I suspect that the values passed around are not what you’d expect.