It seems there's a bug when trying to edit workspace through the sidebar. Same in Developer version.
After right clicking workspace's icon and selecting 'edit' there's no edit dialog appearing but workspaces list is shown. So 'edit' particular workspaces = 'manage workspaces' in this case.

*It works once after browser starting but doesn't work later when trying to edit for the 2nd time. Another issue here is that if I closed the sidebar setup pane with 'edit' popup left open, later I right click another workspace to edit it shows the previously opened dialog what confuses a lot.

**Sometime after mentioned manipulations the sidebar setup opens blank (restart is need to get it back ).

***Checked the things in pre-One version and all is fine there, works correctly in all the cases.
**** Also, there's a bit too much space is reserved next to the setup pane's right edge (too wide shadow effect or smth. else) where the pane doesn't react for closing by clicking outside. So the screenshot shows the panel won't close if I click here.
