The precise setting to control noise amplitude will depend on the activity being performed (unfortunately). On Filter>>Noise>>Fractal Noise, it's "Amplitude". On Filter>>Noise>>Absolute Magnitude Noise, it's "Noise magnitude". And so on.

The right-hand part of the program status bar (bottom of the window) shows the mouse position to the left of the colon and the surface value to the right of the colon.