I copy/paste the “green part” from bar 13 (3/4) to the second beat of bar 33 (4/4). Insert mode is off.
Surprisingly I lose the “triplet” .
Its no big deal, 
I can put it back very quickly but I thought you might like to know as a more complex case might be harder to analyse.
Project file is before copy/paste
MicroSonata1.dorico (1.8 MB)
If one does not explicitly select the tuplet (number and/or bracket) one cannot paste it.
Interesting and Well observed.
I selected the green part by choosing the note or rest at the left and right hand end and pressing “control-shift-A”. But yes, that doesn’t explicitly select the triplet - (which does surprise me. )
True enough, but selecting entire measures by checking the select checkbox in the system track will copy hidden tuplets. However, if one is copying one staff at a time for example, then it is best to unhide (ctrl-H for for me)
As you note system track select is best, but here I only wanted the green voice. What surprises me is that “control-shift-A” on a sequence of pitches and durations would exclude a triplet marking: given that the durations require the triplet marking.
Its an idiosyncrasy, but one I can live with. I’ve survived 20 years of Finale’s triplets
