Can't get Thumb tab on the sidebar to show up

Hi and Seasons Greetings,

I use Defense Connect Online (DCO), so this may be a function of a downstream application.

I am presenting larger and larger presentations and need a way to jump back and forth on slides quickly. The outline view doesn't show slide #s, relying on the title ... that may be some generic wording if the creator didn't make the slide right.

The thumb tab view *might* be useful, but I can't get it to show up.

I see the following in help articles:

Note: If you upload your presentations directly from your computer and into a meeting, the Thumb tab is not displayed. Adobe recommends adding presentations to a meeting from the Content library.

So I uploaded a presentation to "My Content" and used that in the meeting, but still no thumb tab. I see "Shared Content" as a choice to share a file from, but I cannot find how to load anything into "Shared Content". Is there another "Content Library" I am missing?

I appreciate any help.