Clicking the (v) in the top-left of any program window without moving your mouse results in 'Close' being auto-highlighted in the menu that appears if the window is located near the bottom of the screen
Tested in Xubuntu 22.10 but it occurs in older Xfce OSes as well (Manjaro Xfce 21.3.7, Mint 21.0, Xubuntu 22.04, Mint 20.3, etc)
Simply put, if you move the program window near the bottom of the screen and then click the (v) icon located in the top-left of the aforementioned program window, without moving your mouse cursor at all, it will automatically highlight Close
in the menu that appears.