Add content to a staff: something like "copy - add"

For example, as I pointed out in another thread (Duplicating a line of notes selected with Ctl. click ), add a line of notes to a series of chords. Suppose I have a measure with a melody line of four quarters (in a 4/4 beat) and I want to add a major third interval up , for each of the four notes, and then a perfect fifth up the base notes (the first four ones), to wind up with four perfect major chords in the measure. I would be adding notes (not replacing the previous ones) to that measure. One can argue that I could do that just by adding the thirds and the fifths one by one. Sure, and that's how I do it now. But if I could have that first melody line (and it could be a lot more complex that just 4 whole beats), copied to an empty measure, have it transposed a third up, copy it again and bring it back on top of the first ones, by adding, not replacing. Then repeat the process for the fifths. That could save effort and avoid errors. But it means I must be able to ADD material to an existing staff.