Poor focus management in mixer

Open mixer, open drop down with instrument.
"Go" to the desired instrument by typing the first letter of its name (possibly several times, if the instrument is not the first one in the list beginning by this letter).
Until then all good.
Now ... try to select the instrument without the mouse.
[tab] ... nope doesn't work, do nothing.
Oki, let's try [enter] then ... worse: it enters system break on the score while a drop down in the mixer has the focus ?!? But the drop down list has been closed with the selected instrument so you could think that was the thing to do while in fact the score has been altered.