how do you hide only a highlighted section
and how do you assign the each sections into the hidden groups
There is no way to hide some objects for now. Maybe in some next version, ask for it in the wish list :-)
The best solution (yet) is to create a separate staff containing rests until the measure you want to play "hidden" things. Name that staff "Hidden" for example.
To hide that staff, open the Page Setup (menu File, Page Setup), select the "contents" tab (left most), and un-check the staff named "Hidden" (or whatever name you gave) in the right list.
Hope this is clear,
Dominique