That is pretty sweet!
I'd love to have that on my jeep rock crawler. We'd try for 90 degrees.
The last menu option "info" allows you to choose which information is shown. Transmission temp is an option.
Which model do you have? I haven't seen the ability to add transmission temp to the information list on the Denali. Honestly though, having it pop up in tow/haul mode is good enough for me. That's really the only time I need to monitor tranny temp.