However, the “force duration” workaround does not work for me, because the music here is in a time signature of 3/4. The notes are forced to tied notes even I re-input them with “force duration”. Also, there are many such tremolos. Replacing all of them is time-consuming.
“O” engages Force Duration
“66” gives a dotted quarter as note value — 6 for the quarter, and double 6 for the dotted quarter : for all rhythmic values, you can get the dotted value by pressing the number twice — and it’s very handy!
And since you say you have a lot of them: you can do it all at once by first selecting as many tied notes as you want. And you can also apply tremolos to multiple pairs of notes at once with the Shift+R popover, by typing 32 (3 for three strokes, 2 for two notes).