Today I noticed while reviewing suggested edits that someone had helpfully suggested a tag wiki and excerpt for top-bar.
I improved (er, in my own biased opinion) the suggestions, and I wrote in both that the top bar is a panel (it's just a panel in a particular place, I thought, though I may be wrong, and please correct me if so).
Is there any reason not to synonymise top-bar to the much more populated panel? It seems a good idea to have a tag with the name top bar since it's a common term for the panel at the top of the screen, but I can't think of any reason for it to be a separate tag. What is displayed in any particular panel varies by DE and over time, so the exact content of each panel can't be thought of as standard, I would think.