If you just want to check the temperature for filling, Inpa is easier and faster.
From memory, after selecting the transmission module, there are Analog1 and Analog2 buttons. Under one of those, you will see the temperature of the transmission.

If you prefer to work with GT1/DIS, there are procedures to check the level or fill the transmission.

Here is a 'copy'n paste' of the notes I took while exploring DIS in preparation to my future transmission oil change:
HTH

Oil level adjustement with DIS:
- Main
- Select Diagnostic
- Select E53
- all modules will appear, just click the Right arrow at the bottom right
- Select 'Function Selection' at the bottom
- On next screen, select 'Service Functions', then 'Drive'
- The pop up window will show: 'EGS Transmission control' ; select YES
- Select 'Transmission Control GS1904'; then 'Calibration'; then 'Oil Level'
- Click Right arrow at the bottom right
- on the next screen, select 'Test Plan' at the bottom and answer NO the the question about
the Short Test.
- on next screen, make sure 'Oil-level adjustment is highlighted, then press the Right green arrow
- on next screen, select '1' for 'Oil Level Check' or '2' for 'New filling after removing pan'
- Follow the instructions