Over the weekend I worked on moving a document I created in OmniOutliner on my iPad to Ulysses. I am surprised that there isn't an easy way to create a clean plain text document out of OmniOutliner. When I try to send a copy from OmniOutliner to Ulysses extraneous text keeps being added.
What I found that worked was sending the document to Google Docs, and then from Google Docs to Ulysses.
There is little documentation on creating documents based on an outline first created with OmniOutliner, which is surprising because I expect this to be one of the main use cases. In fact, I think that OmniOutliner ought to be smart enough to translate outline levels to markdown heads just as it does with HTML. I suspect that the Mac version of the app does this and that the markdown export type is just not included with the iOS version.