Apps Box by basarafire is one. I actually found his website but it's in Japanese. Google Translate does OK but I don't find a contact point. I'm pretty happy with that. I just would like to ask whether any improvements are coming. Like, is there any possibility it could handle books and docs as well as apps.
OTOH, there are two versions of Collections for Kindle Fire which do nothing at $3 a piece (just as the reviews warned). And then Book Collections, which almost sort of works, also at $3 (and also warned).
I'd definitely like to open a channel to those folks. And they have enough negative reviews that I'm not sure they care.