JasonPetty,
So, you are at the following: System > Phone-Related Information > Key Assignments > DSS/PKM
You perform a right-click on the right-hand side of the screen in an open gray area? You do not see the [Add To DSS/PKM List...] popup?
The only thing I can think of is that you already have 20 of them and it won't allow you to add any more unless you want to push your system and add it via On-Line Monitor; which I don't suggest.
Thanks,
TE