Hello Michael
Can you not edit the existing connection but instead of pointing to the BAR3 cube change it to the BAR3-TEST cube. When you do this you will be presented with a list of all workspaces that use the connection and do you want them to be updated. Choose Yes.
Now when you open the workspace it will be using the BAR3-TEST cube.
Of course, just repeat the process again if you want to go back to the BAR3 cube.
Regards