I used to map bad blocks with qbtools few times decades ago, when diskettes were expensive. nowadays they are very cheap and most people stopped using them completely. perhaps dd diskettes cannot be found so easily, but for games and other not important stuff, writing temporarily to hd should work.
so, my advice is to just toss them. besides, there is a chance they might damage the floppy drive (depending on cause of bad blocks).
to test the diskettes, I usually do erase in xcopy, then format (no verify), then check.
if any tracks are bad, bin it..
also, if too many diskettes are bad, you should check/clean the fdd heads. perhaps it collected dust or something.
