>What I would love to see is a project-centric system, where I can tab between projects and have all the relevant applications and documents appear and disappear with it.
Linux! I'm a Windows dev now and miss Linux so much.
What I used to do back in the day was simplistic, but still very useful - I'd have multiple desktops open, & have each project on its own desktop. SSH connections, code editors, network drives, VMs whatever. It keeps visual separation between environments, even if not total logical separation.
If you need better separation, you can have multiple sessions open at once with separate window managers, user accounts, file system roots, whatever you need - at the same time. I'm hazy on the implementation details but I've seen it done. Altho, this might be a bit old school today, with VMs taking less resources and stuff like docker existing.