Is there a way to have a button trigger a switch to the expanded Control Strip?
Currently I think this is not possible with the system expanded control strip. However it would probably be relatively easy to create your own expanded control strip in BTT as a group - then you can use the "Open Group with Name" action to show it however you want.
I also couldn't find any way to use a keyboard combination to trigger the expanded control strip.
It would be cool if someone would create a preset duplicating the standard expanded control strip.
In any case, it's only two touches instead of one to get to the system expanded control strip.
See my AquaTouch v2!