A useful feature in the word processor: An option to quickly select outline 
level to view. 
In Calc you can group rows and/or columns, creating a nested outline view.
In Writer, you can send the entire outline (that's all paragraphs defined as 
outline style, i.e. all headings when you're using default styles). 
- I'd like something similar to the Calc group collapsing, where I can select 
the outline level on each group/subgroup individually. 
- A different approach would be a level selector, to set all branches to 
collapse at the same outline level. 

The two approaches are not mutually exclusive. 

- Further: it might be useful to have the option of either regarding "non-
outline" text as being the lowest level (so it collapses first), or regarding 
it as belonging to the outline level of the last preceding header.