In my original MS, I have a horizontal line above and below quotes. It’s basically a table with only the top and bottom lines being drawn. In Scrivener, I don’t see any ability to control table drawing like that. Is there another way to draw a horizontal line that will fill margin-to-margin?
There isn’t currently a feature for this, no. You’d need to add it after compile, in a word processor or an epub editor like Sigil, depending on your final format. If you use a unique string to indicate the breaks within the project, you’ll be able to search and probably run find/replace on it quickly (certainly in something like HTML you could, since it’s just text code replacement; I’m not sure how Word handles this, but I suspect there’d be a way to do it.) If the horizontal rules are to go between certain types of documents–e.g. it’s a separator between each of your text documents–you can enter your indicator in the “custom” separator in compile, rather than adding it into the text documents directly.