This is a tricky question because this sort of feature crosses over
into the LDS Gospel Library's functionality space. We want to be a
citation index, not an alternate version of Gospel Library. They're
working on making highlights sync with your LDS account, which would
be more powerful in the long run than just having highlights on the
device where you do the highlighting. However we publish historical
materials (1970 and earlier) that don't appear in Gospel Library
currently.
Since our web site doesn't have highlighting, this isn't a feature
we've ever talked about putting in the mobile app. When we meet
again, I'll talk with my partner about this.
- Steve