If you go into Options > Advanced Settings there is an option to turn on "Export as html using markdown syntax" which gives you the ability to include bold, italics, underline, and strike through in your exported file when using markdown syntax. Click the question mark by the toggle for more detailed info and instructions. I don't intend to add any additional formatting options, sorry about that. I may add visual customization for line spacing in the future, but it won't affect the output of the document.