Q. I did a Bilateral Migration from Bookmarks Document A to Bookmarks Document B. In Document A, I have this folder with 5 bookmarks in it. But in Document B, the corresponding folder only has 3 bookmarks in it. Why didn't Bookdog migrate the other two? Answer. Probably because two bookmarks with the same URL already existed elsewhere in Document B. Bilateral Migration syncs the two documents to make sure that they all have at least one of the each URL, but it will not move any existing bookmarks.
Q. OK, smarty. Then how do I get what I want? Answer. If you wish for, say, your Safari and Firefox bookmarks to not only have the same bookmarks but also have all the same bookmarks in the same folders, then, after performing the Bilateral Migration, you must perform the additional step of a Unilateral migration, set to DELETE All. On the left side of the Unilateral migration, choose whichever browser, Safari or Firefox, has the better folder organization that you wish to copy to the other.
Q. Well, why do I have to do two steps? Answer. Once you've got the same folder structure you want in both documents (by doing a Unilateral:DELETE migration), bookmarks added in the future will by synced to the corresponding folder using only Bilateral Migration. Bookdog's Bilateral Migration is designed to be a "minimally disruptive" operation for copying added bookmarks between two documents. It may be performed daily or weekly. But if you move or delete bookmarks from one document, you must again perform a Unilateral Migration to the other document.