I agree that the library really needs to be improved. I have games (from this bundle and from previous ones) that I have a hard time finding because there's basically no tools for navigating through the things I own. I hoped that the desktop app would be better in that regard, but it has just as few filters for my library as the webpage does. I'd appreciate it even if I could dump my library to a spreadsheet (or csv) file and look through it there.
Alternatively, the normal store/browse page could just add a filter for owned items and call it a day, since all of the search/sort features I'd request are already implemented there.