I'm new to EYB, and am loving it. But, I have the same question.
I have my personal recipes in Mastercook. I've tried using Bookmarklet, but appears it isn't allowing me to paste from this source (I can do it manually). The value of a CSV file would be that rather than needing to manually copy over hundreds of titles, I could produce an export in 5 minutes and be done.
I get the complexity of needing to maintain the integrity of the database - but, even if I could just import titles and source, it would give me a base with which to then update other data. I see the post is a couple years old. I don't know if any progress has been made here