The Threshold Panel is where you set the velocity sensitivity parameters for your entire drum, as well as turn on/off the auto-level feature for sensor input gain.
It is an important feature for handling crosstalk and the overall feel of Sensory Percussion.
The horizontal red dotted line lets you filter out crosstalk by volume. It’s often easiest to hit the drum (or otherwise activate the loud nearby source) that is causing Sensory Percussion to misfire, then move the red dotted line above the unwanted hits. Then double check that it is still recognizing your quiet playing. If you are experiencing crosstalk that is more difficult to filter out, read more here.
The velocity I/O section of the threshold panel allows you to customize a velocity curve for the entire drum. There are common use case presets on the right side of the panel. This will affect the way the whole drum responds to velocity, so if you want specific samplers to respond differently you can adjust that in sampler velocity i/o panels.