ginacc I bought a GX-100 a couple of days ago
I haven’t yet set up my midi patch changes but it does indeed work
In the In/Out Settings select Midi
Set your channel to Receive
From this you can use the typical midi such as bank-program change etc
Or
You can configure midi patches within the GX-100
for example patch 20 doesn’t have to be program change 20 it can be reconfigured to any number if that suits better
The manual can be downloaded from Boss website in PDF form