I wouldn't say change your workflow if you're happy, but I'll answer anyhow!
I also actually tried cmux, but I didn't like they way it did tabs. I like my tabs top-level and not inside panes (but I realize this is a personal choice).
We also do good GH native integrations (linking PRs, showing statuses, and linking GH issues).
We also do AI status indicator even for non-focused terminal panes.
You can also manually mark a worktree as 'unread' (kind of like a star in Gmail)
In addition Orca has a built in file viewer, search, git diff viewer (see all changes like VsCode does)
Also cmux is Mac only (doesn't matter for you, but for others)
So tl;dr -- alot of small things. But those build up for me in a tool that I basically find myself living in
There's a few open issues/PRs that I'm working on getting in! Feel free to drop any request there (it's the best way for me to track it).
For UNREAD messages... Sadly, I'm not sure that Slack has an official API for that. There may be an "unofficial" API there that we could discover, but I'm hesitant for adding support there.
With that being said, it's not that I wouldn't entertain the idea (it would be REALLY useful) but it would require a bit more thought.