From Versatile Monkey Wiki
HoneyDew can import and export to plain text files. These features are found on the menu in the Settings screen.
The format for importing and exporting should look like this:
Category 1 Item 1 Category 2 Category 3 Item 2 Item 3
Anything that is left justified (that is, it has no spaces at the start of the line) will be entered as a category. Anything indented will go in as an item under the previous category.
This format applies to both importing and exporting. When exporting HoneyDew will generate a pre-populated email message with the contents of your list. When importing it presents a plain text box that you can paste your list in from other sources (such as copied from an email).