Not sure what you want to accomplish.
Visual pinball is the system you selected in settings.exe from pinballx.
Visual pinball will load your vpx tables. VPX = visual pimball 10 (x=10)
System lists are a subset of a main system. When you create a system list for a system, you can select them in the main program by selecting it from "select databases". Make sure that "hide custom databases" is unchecked.
If you have selected the system list database file, you can add the tables to it, in the same way you add it for a normal system
I hope this make sense (and if so, i will update the documentation a bit to make it more clear"
Just a question from My side. Why do you want to use a system lists ?