In the animation effects settings panel, while the first 2 drop-down option
lists can be operated by cliking anywhere on them, the "speed" drop-down list
works only if you open it clicking on the arrow button on the right of the
option description. This happens also in the "speed" drop-down list that is
placed at the bottom of the dialog window containing the effect list that is
opened pressing the "add" or "change" buttons in the panel.
The necessity to aim at the arrow is annoying especially since you instinctively
(it works with the other 2!) click on the rest of the visible drop-down list and
nothing happens, then you remember this list is working only if opened with the
right arrow and try again.