Currently we have the ability to see somewhat of an outline with the various headings we have when we select the three horizontal lines on the top left of the sermon document. We also have the ability to select certain sections of text and put them in 'Handouts' and 'Questions.'
I suggest outline marking. After writing my manuscript I highlight maybe the first sentence on a paragraph and 'mark it' as a main point. Any other text that I highlight as sub-points goes under that main point until I mark another line as a main point.
There could be multiple levels of sub-points, all marked with keyboard shortcuts, and then you could have an outline from your manuscript all in the same document.