You need to search for the Mix Level you want to control and map it to a Hotswitch. Using Program 1 Clean Ambient as an example, enter the PARAMETERS menu and hold down the P LED button until you enter the “Hotswitch 1” programming menu. Press the B LED button so it shows you the Preset B parameters (reverb parameters). The first one should be “Mix.” That will control the mix level for the reverb in the Program. Press the first quick knob to assign a value such that whenever you press the Hotswitch 1 button in PERFORM mode the reverb’s mix level will go to that value.
Repeat these steps, but the second time around enter the Parameters menu and press and hold the A LED button to program Hotswtich 2; the third time around press and hold down the B LED button to program Hotswitch 3.
After this process you will have mapped 3 different Mix levels of the reverb in the program using three different hot switches. During your performance you can keep your H90 in PERFORM mode where these three hotswitches are accessible all the time.