SUMMARY It would be very convenient if the "Enter" button just triggered the "Apply" button. Right now, there are to possibilities: a) Use the mouse and click on it b) Use Tab to move from control to control until the Apply button becomes active and then press "Enter" As "Space" corresponds to "click on selected setting", it wouldn't interfere with "enter"
There's actually already a functionality: "Alt + A" to focus the "apply" button. *** This bug has been marked as a duplicate of bug 449337 ***
*** This bug has been marked as a duplicate of bug 440255 ***