When workspaces are no longer relevant, they can be deleted by a workspace admin or a Subscription Owner. To do so, click the
v icon to the right of workspace name at the top of the sidebar and select "Edit Workspace."
You can access your current workspace's preferences by typing Ctrl-Shift-W.
From here, click the red "Delete this Workspace" link at the bottom of the dialog.
This will take you to a confirmation form where you must enter your password before clicking "Delete Workspace" to confirm the deletion. Deleted workspaces cannot be recovered so be absolutely sure you want to delete them before doing so.