Some of them are hard coded, like in the skin browser. When you open the skin browser and have a S definition it is populated from the RideRunner\Skins folder.
For Directory lists you can define you direcrtory as in
SD,00,03,32,32,"$Backgroundpath$","*.jpg", this will load the list with the pjg files in the
Backgroundpath definition. BackgroundPath=C:\Program Files\RideRunner\Backgrounds.
If you have a Text file with info like Audio, Radio, XM, Video saved as List.txt then you can use a CL (CustomList) and populate it from that text file with a Command
And of course lots of reading...