Once you've got the notes just about right and start adding extra stuff like expression/technique text, articulations, hairpins, pedalling, lyrics etc., the new graphics often clash with what's already there, which can get really annoying.
I find that just about everything I insert ends up on top of a notehead, stem or leger line and I have to shift it. To add insult to injury, the thing you want to shift is often so obscured that you have to zoom right in to find it again.
Wouldn't it be neat if the extra gubbins were positioned a little more intelligently?
A bit of conflict avoidance would be nice
Adobe InDesign (desktop publishing) has a layers and lock-out feature. One may create up to six layers and lock each one individually that way you can edit a graphic without disrupting the text or you may edit the layout without having to re-adjust the text etc. Perhaps this type of feature would work for your problem in Sibelius and is worth adding to the wish list.