I have a similar, but not exactly the same question, maybe somebody can help me either: I want to have ONE duplet consisting of two half notes instead of a dotted half note (3/4 time, too). I thought I’d just enter 2:1.5 into the tuplet popover, but this just gives me a duplet of the length of one half note (bug?). The complicated workaround described above (a hidden quartuplet with two duplets in it) works mostly, but I have not yet succeeded in hiding the rest(s) in the next bar.
Thanks for your help in advance!
EDIT: I found a way: I can nest a 2:2 tuplet of half notes into a 4:3 tuplet of quarters and hide the quartuplet as described. So, for the moment I have a solution but it neither looks good by default (bracket uneven) nor this is a really convenient way of inputting these. If there is an easier way, let me know!