I doubt this is what you want, but it's a workaround that may be helpful.
The track number is always related to where the track is in the track list.
Let's pretend you have visual audio on tracks 1-3, and then 6 & 10. All tracks between those tracks are hidden.
If you click on the track control area (left side of the track) and drag up on track 6, then release it when you see the blue line above track 6 (almost immediately), it will move that track to Track 4. Do the same thing with track 10 (drag up a tiny bit) and it will get moved to "Track 5".
Now all your visible tracks are #1 to 5. Those first 5 tracks will show up on the cs18ai as the first 5 faders.
The other tracks being kept just for "safety" reasons are below. In the rare cases where you need to work with one of the hidden tracks, unhide it and drag up to be next to the other track(s) as desired.
Not your specific request, but dragging the tracks up takes 10 seconds to move all visible tracks into a sequential order.