[itsme]

What you need are "Song" entries in your library that look like the one in the screenshot. One entry for every song that you want to play from a specific book all referring to the same file, but having different title and page order entries. The file exists only once on the tablet and the songs can be used as any other songs. I use this all the time without any problems.
In your case, as your book already contains PDF bookmarks probably the easiest way is like this:
- from the "Songs" tab click the button "Import".
- A dropdown menu opens, choose "CSV or PDF Bookmarks"
- navigate to your book's PDF and select it
- a window opens, entitled "Select Songs to Import" that shows the bookmarks of your book's PDF
- check the checkboxes of the songs you want to import and click OK
- that's it
There are several other ways to create such songs:
- "snippets" as proposed by skip
- import the file once and edit title and page order for one of the songs it contains, then copy the song and edit title and page order of the copy to show another song
- prepare a list of the songs in the book as a .CSV. This can contain a lot more information as PDF bookmarks and is used in the same way, as described above