Just a hint to those who are still looking for the best way of entering durations: being able to redesign the key commands lets you choose the preferred option for all the duration and articulations keys.
As for duration, I first decided for a scalar placement: notes with flags in the first row, without flags in the second row:
U (1/4) I (1/2) O (4/4)
J (1/32) K (1/16) L (1/8)
Then, I decided to keep all the most often used keys as near as possible. So, I decided for a circle placement:
U (4/4) I (1/2) O (1/4)
J (1/32) K (1/16) L (1/8)
This way, I continue to have the faster notes in the most accessible row, and have the very common crotchet just over the quaver.
I keep them all in the right half of the keyboard, at easy reach from the duration keys, and next to the easy reference of the Return and Backspace keys. Nothing on the left half of the keyboard, that I want exclusively devoted to note pitches and chords.
Just left of the Return key: Force Duration, +Shift: Lock to Duration
Immediately on their left: Insert on/off
Just left of the Backspace key: Staccato, +Shift: Staccatissimo
Immediately on their left: Accent, +Shift: Tenuto, +Shift-Alt: Staccato/Tenuto
7, 8, 9: Natural, Flat, Sharp
Under the duration keys: Rest on/off, Value Dot, Tuplet
On the left half: Note Pitches corresponding to their English name, Q for Chord, S for Slur, <> for Hairpins, R for Repet, F for Flip.
I should reserve a shortcut to Acciaccatura and Appoggiatura, but my preferred positions don’t work with my keyboard layout. So, I’m still thinking about them.