I've just started using Denemo two days before, and first of all I want to congratulate the developers for the excelent work they have done :)
I've started using Denemo to adapt a piano music sheet (two voices, two steves with different clefs) into a guitar one (one steve, one clef). The only problem I'm having at the moment is that I don't know how to get the stems of the first voice going up and the stems of the second voice down, in order to distinguish easily voices.
It's more difficult to read and looks untidy in the way it shows, because I get stems of one voice crashing with the ones from the other voice (and I get complaints from Denemo when doing a print preview).
I've been reading at this page (http://denemo.sourceforge.net/Frog/polyphony.shtml) some examples and the point seemes to be the \stemup and \stemdown commands, but I don't know how to put it in the Lilypond output without error complaint. I've seen also that there are menus in Denemo with this labels, but they don't do it, looks like a bug, or i don't know how to use them...