Where can I learn more about the auto-inserted expressions?

Here's what I've got going on:

Garritan Orchestral Strings  Violins KS

Above the first note that I mark as "sul tasto", two invisible expressions are auto-added.

The names are HP:KS=11  and  HP:KS=11:Off
In the expression Selection pop-up window the Playback info for these expressions is:
Type:  Dump...
Set to Value: 0