In Discover, if you hit the "X" on a workspace tab, it should warn you and ask if you are sure you want to close the workspace. The "+" button to add a new workspace is right next to the "X" on an existing workspace, and it's easy to hit the wrong one. With the new carbon-colored background, the "X" blends in and cannot easily be seen. I've accidentally closed a couple of workspaces without realizing it and have recreate everything that was within them. A simple confirmation box would have saved me the trouble.