Note: I have jumped in on this topic because I went to the forum to post the same question that Adam did, and saw he already had, just minutes earlier. Rather than re-asking in a new topic, I figured this was better.
Perhaps answering this question would help us: Is there any way to open the panel other than putting a button on the page, and adding the Open Panel action as a Click event for that button (or add Open Panel as an action for some other event)?
Like Adam, I expected to see a tab on the outside edge of the Panel, like is in the Visual Builder, when testing the app.
To reproduce it, just add a Sliding Panel to any page, then Test the app.
Visual Builider, with panel open:
Visual Builder, with panel closed:
In a browser, after clicking Test:
If you intentionally did not put a tab on the panel in the actual app, then please consider this a feature request, to have it there, and, possibly, make it optional (a "Show Tab" check box in the Panel settings).
Thanks.