This can be done using a HotSwitch. Check out this section of the user manual that explains how to do it and let me know if you have any questions: https://cdn.eventideaudio.com/manuals/h90/1.9.7/content/edit-modes/parameters.html#hotswitch
You can use the onboard footswitches in Perform Mode, or Program a MIDI controller to turn the HotSwitch on/off.
