[photex]

TMUX is a transferable implementation of terminal session and "tab" organization. It's also scriptable if you aren't happy with some aspect of it's default presentation or interaction. For me, that is enormously valuable.

Sounds like your use case could be mapped by TMUX windows acting like Terminal tabs, and TMUX sessions acting like multiple Terminal windows. Except the benefit is that now you can use this workflow on any system with a posix compliant shell and a tmux binary (which I'm pretty certain is practically all the things at this point). Sessions and windows can be given labels which is a nice touch too.

If you are an Emacs user, it's also worth noting that TMUX totally works well with ansi-term. :) I normally have a TMUX session dedicated to an ansi-term buffer in Emacs. Even if I have iTerm or Konsole using another session.

"..but transient windows don't need splits"; well, in my universe transient windows are splits. :)

Anyway, I don't want you to think I'm trying to persuade you into adopting what I consider awesome and useful. Just clarifying my statement. It sounds like you already have a workflow, are happy with it, and don't see any need for alteration.

[eridius]

I use tmux over mosh on my Linode. I've just never found it to be particularly useful on my local machine. Especially because it removes the ability for my terminal to manage history and requires using a keyboard shortcut in order to scroll backwards in history.

[phaemon]

I believe Terminal.app handles mouse events differently, so the standard tmux config doesn't work right. Maybe see if https://bitheap.org/mouseterm/ improves matters for you.

[eridius]

Terminal.app doesn't handle mouse events at all. I filed a radar for that a while ago. But I don't consider that good enough reason to use iTerm2 as the programs that actually support CLI mouse events are very rare.