This snippet should show a tremolo consisting of two dotted crotchets separated by a triple beamed tremolo mark, whereas I'm currently getting a beamed tremolo with two dotted quavers.
I think it would be possible to fake the desired output by drawing two dotted demisemiquavers, i.e.
c32.*4 e32.*4
then shortening the beaming, but I'm not quite sure how to achieve the latter.