I haven't tried this, so I don't know if it works, but apparently this is what you do:
* Gear menu in upper right
* Administration menu item
* Dimensions icon
* Workspaces list
* While hovering over the line of the Workspace to delete, click Delete on the right.
I believe the manual/wiki hasn't been updated for version 2, so it's probably only somewhat helpful/accurate.
From reading this forum, it looks like there are a lot of problems in version 2, so if you haven't entered a lot of data already, I'd consider switching to 1.7.5 for the time being.