If you have several windows open, the "x" icon for closing the last window disappears behind some tab-navigating arrows. I find myself constantly clicking "arrow-right" of the tab navigation to see and use the "X". Very annoying for example if I'm repeatedly opening and closing windows from a lengthy "Find Database Objects" list.

We'll check it out. Note that you can also Shift-Click on a window tab to close the corresponding window.

Ok. didn't know the shift-click, that helps.