Hello! To my knowledge, a character can only be assigned one particular folder, but one way you might be able to achieve what you're looking for is to use flattened folders. Here's an example of what that looks like on my account. You can set the parent folder's display style as flattened when creating or editing it, and it will display the contents of all folders within it when viewed. This only works for parent + sub folders, though. Alternatively, you could make use of folder descriptions and insert links to each of the characters in the description of the parent folder (or other side folder); but you'd have to update it manually any time something changes. I hope this is of use to you!
Is there any possible way I can get a single character to appear in multiple folders?? Especially having a character appear in a parent folder + a sub folder. I think it would look a lot better if once you clicked on a folder you could already see the character(s) in the parent folder without having to go to each individual sub folder but I have no idea how to do this or if it’s even possible.