Hello, sorry about the bad experience. Could you be more specific about the problem and what you were doing when it happened ? The add-on is doing nothing on the bookmarks themselves, it just displays them. It is doing something on a bookmark only when you decide to act on it, and then this is only affecting that bookmark, going through the FF bookmark API's. So there's very little chance to corrupt anything, and this is very limited in scope. I would need more details to understand what happened and to correct if there is any bug indeed, and would be grateful if you can share more.
Let me know here, or best would be to report on https://github.com/aaFn/Bookmark-search-plus-2/issues if you are ok to do that as it is better to exchange and track correction.