@David-Healey I suggested this snippet in their other post about this, but I've never used it so can't advise on implementation:
https://forum.hise.audio/topic/14397/hihat-open-e-hihat-closed?_=1771175779155
Have you used it?
Other post(s):
https://forum.hise.audio/topic/14397/hihat-open-e-hihat-closed
https://forum.hise.audio/topic/14404/dificuldade-para-o-hihat