Per support...
Assume a grid of customers
You have customer a, and customer B
If you click on customer a in the grid, it will open a new tab for the form for customer a
Reactivate the grid
If you click on customer B, it will still open another tab
If you go back to the grid and click on customer a again, then it will now NOT open a new tab for a because of the checkmark
- the tab is still open.
It applies to only a specific instance of a BO