Table of Content / Bookmarks in the new Acrobat Reader

I'm a little confused by the most recent update (continuous release 2023.003.20284).

I'm reading an existing document and looked for a "Table Of Contents" icon... but can't find one.

Some of the articles I've read suggest that there can be bookmarks, hierarchical bookmarks and also a Table Of Contents, and apparently these are all pretty much optional.

• When I click on the "Bookmarks" icon I see only a blank panel.
• When I click on the "Pages" icon I see page thumbnails, but no Table of Contents.

Trying to keep this question as simple as possible (though feel free to elaborate):
If there is a Table of Contents in the .pdf file I am viewing, which icon / toolbar button or "Tool" do I need to use to find and display it?

Thanks very much.