It would be useful if you could click on some standard notation elements in the pdf window and nudge them with the arrow keys: for example, dynamics, tempo markings, and markup. Maybe have a toggle for "automode", so instead of bringing up a menu like the ruler currently does, it just picks an appropriate property and updates the code. This would save a lot of time if there are just a few items in the score that need small adjustments.
I'm obviously coming from using Finale where "nudging" objects is the norm. But I do miss it as a final step in touching up a Lilypond Score.