I’m not sure if I fully understand what you’re trying to do, mainly because the .dorico file looks slightly different on my machine from your screenshot, but I was able to get the rest to move in measure 89. Here is the file
https://drive.google.com/a/chiaraquartet.net/file/d/0B0rreGRZAQNCSGl2bGgtMEdDQVU/view?usp=sharing
To make the rests separate from the notes, I had to do 3 steps.
- give the notes in the chord a Voice column index of 1
- give the natural sign an Accidental X offset of -7/8 spaces
- give the rest an offset of 7 1/4 Y (I saw 2 rests, I moved the lower one up, and made the upper one invisible with opacity of 0)
After this, when doing note spacing, I saw 2 handles and was able to move the notes to the left a smidge, and the rest to the right a smidge.
I’m very new to Dorico, so I’m sure Daniel has a better method, but it is a testament to Dorico that I figured this out so quickly, I think.