Using the down/up arrows accelerates the scrolling through all entries.
It goes much faster compared clicking with the mouse onto the triangle at top and bottom.
Using the up arrow brings you quickly to the end of the list where AES and Phones channels reside.

Some proposals:

1) more function keys

It would be useful to get more functions, something like this
Shift-Up/Down - Scroll 10 lines
Ctrl-Up/Down - Scroll 20 lines
Page-Up/Down - Scroll by page (number of entries might depend on the vertical resolution / number of pixels of monitor)
Pos1 - Go to first channel
End - Go to last channel

2) Selection list compareable to driver settings

Ideal might be a popup window like you have in driver settings for the selection of WDM devices.
Scrolling up and down via the scrollbar and then selecting a channel is even faster.

As the setup and the monitoring channels are usually fix

This is how one could avoid having to choose the same channels again and again "one by one":

3) storing and recalling channel selections as "favourites".

I would define for example
- Monitoring Main Out
- Monitoring HiFi
- Monitoring 1620 Phones1
- Monitoring 1620 Phones2
- Monitoring 12Mic Phones

Other people might want to store their surround channels as favourite.
Then you only have to select your favourites with one click

4) defining default entries for stereo and surround

It would be extremely helpful to define the default channels for instruments
a) for stereo
b) for surround; if you have no surround setup, simply enter the two channels for stereo and leave the other entries free.

Then you only have to concentrate on selecting the instruments and their position on screen.

This might even be quite easy to implement and could save many mouse clicks and deliver most comfort.