I'll chime in here with my take on this.
In Arc, you can 'close a tab' with a single click (there is a "-") to the right of the tab name). This effectively suspends it, in Orion's vernacular. But the tab entry stays in place. If you place the cursor to the right of the tab entry, there is no an 'x' with removes that tab. So essentially, you can close/susprend a tab that you don't want to see but want save for later, then, if you choose to, delete the tab. At that point it becomes part of your history/archive.
