Excel Version 16.17 for Macintosh can create indexes that work with unrealBook.
In Excel, create a new empty spreadsheet.
For column B copy your filename from the Finder or Explorer and paste into column B.
For column A, put the displayed title of song (no commas).
For column C, put the page number.
For column D, put the number of pages of the song.
Choose Save As… and choose CSV UTF-8 (Comma delimited) (.csv) for the File Format. Give it a suitable name.
Send the .csv to unrealBook using Air Drop, Email, Open in…. or dropbox and go to Songs->Indexes and load the index.