I have found that you can "push" a bunch of notes together all at once, from either the front or the back, but I think it won't push the barlines as well, so it's best not to have those, or if you move a barline it'll push all the notes in that measure, but not other measures. If you want to make room for more notes, try the "Insert measure" option under Edit. That will give you lots of space for new notes. Then once you are done, use "Layout" under Edit to get things spaced out evenly. I hope that helps.