I suppose the closest to this is like a standard file explorer in the left sidebar. to have it open the main drive or some directory, where you can navigate the file system. This is the normal activity in coda, and would be like the sidebar in windows explorer file manager.
It would be cool to have this as a togglable option in the View menu. So the current ability to show the projects would still be there. When using the file manager you could possibly right click a directory and select "Add as Project" which would then bookmark the directory into the projects area.
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