Creative workarounds:

Maximize release time of the high hat, record a high hat loop and put it into a switch. Then use another module (I tested using snare module), turn the volume, attack, and release all the way down, and connect the trigger of that module to the CV of the switch. Connect output of the switch to the MIX IN pin. Use the second module to turn ON and OFF the high hat in whatever sequence you record for that module. This is hard to control though.

Another idea I just tried, take the trigger of the second module, patch that to the SQUARE to TRIG pin in the top left and take that TRIG pin to the trigger input on the high hat module. Turn down the volume of the high hat to zero. Have the second module trigger control the CV of the switch like before, but now since it’s feeding a trigger to the high hat, if you do a short tap of the second module, it will trigger the high hat with a long decay but then cut off the audio shortly since it closes the switch. If you do a long hold on the second module, this will leave the switch open, trigger the high hat with the long decay, and you can hear the high hat decay normally. This is one way to control the length of the “length of audio decaying when triggering” the module, not precisely the decay rate, but it gets close.

Another idea is to control the delay module feedback parameter. Turn down the attack and decay of the high hat module and turn up the FX send (high hat module volume optional to blend some of the original signal in). Then use CV control to control the amount of feedback the delay has to control the “decay time”. Use a short delay time and tune it appropriately short so it sounds like an oscillating sound source (or don’t, have fun). Then I used a slower LFO to control the amount of feedback which extends the “decay time” of the high hat. If you use the BPF mode, then I found it likes to oscillate very quickly but it’s really fun to throw CV on the TUNE parameter on the delay and get crazy karplus strong sounds out of it. You could use a MIDI sequence tied to the feedback to control when the high hat decays and for how long. You could use a MIDI sequence tied to the TUNE knob to control at what pitch the high hat will decay at. Switching to DBL mode, if you turn the TUNE knob all the way down and the TIME knob to taste while controlling the feedback, you can get a more realistic “decaying high hat control” type of sound. I think this is the most accurate sounding way to do that. Messing with different TIME  and TUNE values while modulating the feedback in the DBL mode with a square wave LFO can generate different sounding high hat patterns depending on the high or low state of the LFO. Could patch the square LFO to the TUNE knob as well to push the delayed hat around in time.

thank you so much for these suggestions – none solved my initial problem ( so far )  but they are hugely inspiring for me!!

the last one is amazing, that is a whole new world opening up with the ENV to FB mod!