Viewing ToC for Audiobook in Books

I'm in macOS Sonoma, so Books 6.4. How can I "open" an audiobook so I can look at the ToC without starting to play it, to play a particular middle chapter, or just view the ToC? I see the "Next Track", Previous Track" items under "Controls", which is a bit clumsy (although not "Next/Previous Chapter" etc.; what's the difference?), and I see the "tracks" button on the upper right (is that all that's available?). But I don't see any way to view the ToC as a whole.

Maybe Sequoia will be different.

TIA, 🤔😉😊