If you want to remove a character from the workspace, it is possible to do so even if it was added from the marketplace. Simply click on the character tile that you wish to remove, and you will be directed to the view page where you can access its details and remove it from the workspace.
To remove a character from the workspace, simply go to the Marketplace and expand the selection. If none of the AIs are currently utilizing the character, the 'Remove From Workspace' button will be available.
When the user clicks on the "Remove from Workspace" button, the selected character will be taken out of the workspace and directed back to the character list page.