If you set up the remote/HUI features for your DAW (assuming you use one instead of a hardware recorder), the track names you've specified in the DAW will appear as 'scribble' strips on the LCD when you activate the Remote Layer. You can then scroll through these in banks (8 or 16 at a time), using the keys in the DM's machine control section.
However, this doesn't happen for out-of-the-box channels - ie - those routed to the DM's physical layers. Therefore, you're stuck with three options:
1. 'Classic' tape and sharpie
2. Simple memorization of the channel layout (it helps to use a standard template)
3. Refering to your DAW's track array to determine DM channel inputs.
Some engineers also use track sheets - a bit of a pain in the neck (literally), but lacking anything else, these are your choices. Best I can determine.
CaptDan