From what I know, one can only add a panel in the Toolbar Panel to an existing workspace.
This makes sense because the Toolbar Panel is meant for a more organized and detailed view of active commands in the current workspace.
One way to work around it is to make a single command and add it to several controls like Toolbar Panels in different workspaces.
Another possible solution is to add a button to the QAT (Quick Access Toolbar) or Navigation Toolbar which is displayed in all workspaces.
I hope this answers your question.
- Erik
