Editing trills

I would like to be able to control the durations of the individual notes in a trill. For example I have a baroque trill in which I would like to increase the duration of the first note (above the trilled note) and maybe also the last note of the trill. It's just a matter of adding nuance. I tried using the Piano Roll Editor (nice feature!) but apparently the individual notes of the trill are forced to have equal duration. Is there another way to do it?