Right now, if you have many buffer tabs open, and you’re viewing in two panes, all the buffers (of both panes) look like they’re part of the same line.
Technically, it’s easy to tell which buffer tabs belong to which pane, since they’re on top of it. But every time my eyes go up to the buffer tab line, and I try ctrl+pgup/pgdown my way through different tabs, I always get messed up by the fact that it looks like one big continuous line.
I’d suggest just putting some kind of visible marker which separates the different panes, which goes all the way up to the buffer tab list.