First, the easier part.  Set Tails On everywhere.  That will keep your effects decaying naturally.  It can be a special effect in it own right, with active swells using [P] In Gain.

Disclaimer #1 –  I don’t use Global much with an expression pedal. MIDI & Aux?  More often.  I could be wrong, but I haven’t found a way to carve out a specific range of the target parameter internally.  So, a steady foot to hold on a parked position, plus steady physical pedal.

Or – for the example below – you might suddenly find yourself in +12.0 dB boost territory.

Disclaimer #2 – So far, I haven’t found a method to fulfill your Bypassed requirement, except for one workaround.  And I don’t know if you’re going to like it …

I’m not saying there isn’t another way, but here is what I came up with, after trying out a few things.  Enter System settings – Global – dial Quick knob 1 to [P] In Gain – exit.  The caveat is … (P) Mix has to be at 100%.  You’d have to re-Save your Programs with that.  I haven’t tried everything, so my concern is that …

Disclaimer #3 – Your “dry tone” may end up with some degree of coloration.

In any case, here is a link for the Global Mapping chart.  I’ve been testing out some combinations of Mix parameters, In Gains & Out Gains for both (P) Program and the (A) + (B) Preset parameters ganged together.

https://cdn.eventideaudio.com/manuals/h90/1.7.5/content/appendix/global.html