How to adjust horizontal distances?

Where is a setting to decrease the minimum horizontal distance between notes?
I can compress the width the bracket " { " shortcut (or Menu > Format > Stretch > decrease layout stretch).
But often I would like to compress more (to avoid line breaking early). Is there a setting do define the size of the myterious "sp" unit (all style settings relate to this)? or settings to
a) allow notes more dense, and
b) setting the standard a little narrower, to aviod frequent need of the above mentioned shortcut.