I have the habit to use CMD-Return to confirm dialogs, possibly because I use it as the default to send messages on Slack. Anyway.
When I hit CMD-Return while in the link-naming window, it hides/show tabs. It’s definitely not the behavior I expect. In fact, nothing should happen and I should break my habit of CMD-Return instead of just Return. (Nothing happening is what happens in a Save As dialog.)
It’s hard to see in the GIF above, but the Edit menu flashes when I hit CMD-Return, which suggests that the Navigate menu gets activated.
Note that ⌘-[Return] is the shortcut for Note ▸ Navigate, which follows the highest-priority outbound link. But I don’t think that’s involved here, either.
Looking at the code, this does not appear to be a mistake; Navigate toggles the tab bar if the window has the focus. If the text pane or the view pane has the focus, Navigate has its customary meaning. It’s been that way for at least three years, and possibly much longer.
I wouldn’t be surprised if this arose from some very old forum request!, Perhaps someone else remembers?