I’m about to send my manuscript to a friend to read. Is there a way for his edits to show, similar to MS Word’s setting Review/Track changes?
Yes, there is a Revisions mode - see from page 476 of the manual (in the Help menu) for more info. It is a bit more limited than Word’'s track changes as removed text will not be marked. But your friend could add a Comment to the text if they do delete anything.
You could also look at using Snapshots instead of Revision mode - so take snapshots of all documents before you send the project, and then use the compare functions to see what has changed. See from page 428 for info on Snapshots.