Summary: when a tab is closed (e.g. alter table tab), switch back to the last tab that was active, not the last tab in the list of tabs.
I often switch back and forth between a query tab and a table design tab. When I close the table design tab, the focus goes to the tab immediately to the left of the table design, which is hardly ever where I wanted to be. It would save many clicks to have the focus go back to the previously active tab.