Oh my gosh!! I honestly can't speak for everyone but I know myself I would DEFINITELY use this feature!!! I have so many characters that belong in the same world but I hate cramming them all into one folder because it just looks so clustered ;-; If we could have one folder but dividers in said folder it would definitely HELP!!
For me, as an example, I have a village setup with all my little Birdfolk and Guumis; plus their deities (in my headcannon) do with the dividers it would be easier with ones such as "deities," "villagers," "wanderers," etc. Plus being able to have a short blurb about them in the dividers so people understand what each section is for.
I honestly believe this would be a HUGE help for everyone, including RPers and Writers on this site ^w^ As well as what you spoke of with selling and trading. It'd definitely be easier to have one folder with each divided section for "selling," "trading," and a "pending" section or even sections of "easy" "medium" etc for the value you place on adopting.
Please, oh please, MAKE THIS DREAM IDEA A REALITY FOR US ALL!!!