For on/off you need to set the assignable switch [ASSIGN 1] or [ASSIGN 2] to be latched and not momentary. If you press the Performance name then select "edit" - it's under this area.

If you press the button and it turns on and stays on and press it again and it stays off then that's already right and set to latched.

Then go to edit the details of InsB. Select the parameter you want the [ASSIGN 1/2] switch to control and press [CONTROL ASSIGN]. Then when the menu pops up, press the [ASSIGN] button you want to control this.

You only get two states on and off - so you may need to adjust the curve so that "high" value is what you want.

Last, you may want to go program the default value that you just had controlled by the assign button to your desired low value. This low value will be the OFF value. Then when you press the assign button - this low value will be offset (added to) according to the curve.

Since this is a binary switch I would probably use square instead of the standard curve such that Source(ASSIGN button)=0 has an output of 0 and then before/near the middle to the end is a fixed high value. The curve would look more like what's actually going on vs. a ramp.

All delays have a Wet/Dry balance and these should be used to simulate on and off.

Alternatively you could move the effect to variation and have the assignable switch increase Var Send (initially set to 0).