There currently is no way to sort the tables. You do have to specify
the zig file once per each ArcMap session when you add layers. The
window does show nonspatial tables but these are marked with an info
bubble telling the user why zigGIS cannot use it. We think this is
better behavior than simply hiding nonspatial tables because some
people might wonder why certain tables don't show up. This goes along
with Joel's "Don't hide / disable menus" philosophy:
http://www.joelonsoftware.com/items/2008/07/01.html
The good news is we have started some work on enhancing the add layer
window. Some of these issues will be addressed in the next release.
-Abe