I made a quick screen cast where I opened up a Room preset that has the Decay knob mapped to the HotSwitch.  Originally, the HotSwitch toggles between 0.59S and 1.83S.  In the screen cast I change it to toggle between 0.59S and 0.0S.

https://www.youtube.com/watch?v=GruBDOll9z4&feature=youtu.be

You'll see that long pressing the HotSwitch literally just means keeping your mouse pressed on the HotSwitch for a second or so.  That's a familiar gesture in the iOS world.  I suppose on the desktop it should also be possible to right click on the HotSwitch to do this, as that's a more familiar interaction in the desktop world.

You don't need to have an H9 connected to create or change a new HotSwitch mapping, and changes to the mappings always get saved with the preset.