Pretty much everyone that has EFI tuning also has the turbo brake function.
Most have multiple tunes on a switch with one having the TB function.
My tune in my signature is the only tune I have, it has the turbo brake function, I use it 24/7 365 leap year 366.
It functions with RPM’s when the rpms drop below about 1800 the TB function kicks off.
Start contacting some of the EFI tuners, starting with Ridge Runner diesel, Danville Performance and Motor Ops.
If your not deleting any emissions stuff then Duramax Tuner.
In your case probably a switch would be necessary, but
Your questions need to be asked and answered by a actual EFILive tuner.
Edge Insight CS2 or CTS2 is only a monitor/gauge nothing else, like what’s already been mentioned.
The only way to add the TB is thru wiring with a switch like you’ve already checked out or EFILive tuning. https://edgeproducts.com/shop/insight-cts2
It’s possible you might be able to switch between tunes with a CS2/CTS2 this I don’t know for sure, depending on the year Duramax, this you’ll also have to asked a EFI TUNER.