Do a bit of Juggling
Use Diaps toolbag to set a assigned P tag to H3 (Each of the item types to be indexed has a a unique class="Onomastics" or class="Movies"
Each item to be indexed has a title=" <stuff you want in the index> if the text in that P block is different than what is wanted in the Index
Build as a fake Contents.
Then make a HTML Contents from that
then remove the Semantic flag (because you only can have one
Contents) line from the OPF <guide>.
Undo that H3 Tag change (back to P or Div)
Repeat for Group 2
And finally build the real Contents
(tweak the other indexes header so they are included)
A bit of a juggle, but sure beats all that typing