Lost in New UI's

I clicked try the new cursor UI and now have two UI’s or windows or two IDE’s, is the idea I switch between them? I couldn’t figure out how to get the ‘old’ VSCode UI back, then suddenly I got it back. I like the idea of maybe two windows or IDEs as I prefer to see terminal / files and folders - although tools like Claude Code have started to make that more redundant.

Where I would like to leverage this dual IDE is to run multiple agents on a project. Is there any documentation on all this?

The other thing is I would prefer to only see the project I am working on in the left nav vs all my projects as that gets cluttered (in the agent window)