All of this, plus it knows what agent is running in which windows and what session that agent is working on. If you have to reboot, it can reconstruct all your terminal setup and restart the agents on the right session automatically.

I was looking into Herdr too, but could not bring myself to switch away from tmux yet (there are a couple of shortcuts that I have in my workflow, which I can't config in Herdr). What I ended up doing was to use the tmux agent sidebar, which, with mouse support, I think does a lot of the same things already.

For me, the main reason is the remote sessions. I can copy and paste text and files in a remote session with no extra config, it's amazing!