A brilliant guy named Alexander Urik showed me this way to open the TP UI via MXS, but unfortunately I can't get it to jive, so will debug as time allows...
on selected TPs
max modify mode
cmdHWND = for c in windows.getChildrenHWND #max where c[4] == "ModifyTask" do exit with c[1]
btnHWND = (windows.getChildHWND cmdHWND "Properties")[1]
(
UIAccessor.PressButton btnHWND -- press the button
)