I have been experimenting with the desktop application and I tend to work with a few tabs of Asana open at any given time. As expected, Ctrl+T will open a new Asana tab, but Ctrl+W closes the entire window and all tabs simultaneously rather than the currently selected tab. I confirmed via the “help” icon in the top left that the keyboard shortcut to close a tab is Ctrl+W, and it also indicates that you can close the entire window with Ctrl+Shift+W which actually doesn’t do anything.
Fortunately, if you hit Ctrl+W and your entire window disappears, you can double click the Asana icon in the system tray and it restores the entire window with your tabs, but this is a clunky functionality that I’m sure is messing with the workflows of other users as well.