I have several Opera ADR files with bookmarks that were created back in 2005 with Opera 7.54. I would like to merge these to one single ADR file. The goal is to convert them all and end up with one single HTML bookmark file that's compatible with all web browsers.
The latest version of Opera, version 12.02 supports exporting to either HTML or ADR, and it can import either HTML or ADR. The older versions could only handle ADR files.
But instead of importing from ADR and exporting to HTML several times through Opera it would be much easier to first merge the ADR files, and then export to HTML.
I did try importing ADR files one after another and Opera just kept on adding the bookmarks one after another. It does not check to see if a bookmark is already there and so it doesn't overwrite existing bookmarks. If it was a good program it would have even prompted the user whether or not to overwrite existing bookmarks. But hey I don't even use Opera anymore... I just want to convert my old bookmarks to a more compatible format.
The most bookmark merging tools I've seen are made for Firefox HTML format. Like the "Firefox Bookmarks.html Merger". I have not found anything similar for the ADR files, something that can intelligently merge and remove duplicates of bookmarks inside ADR files.