It’s worth mentioning that it is possible to create subfolders, but the process is less than obvious. You have to click the + button next to the account you’re creating a folder in, and then specify the whole path. That is, if you want 2021 under an existing Archives folder, you have to type Archives/2021.
While the behavior is here, it’s less-than-obvious (clearly), so the design needs to be adjusted.
The issue of moving folders between accounts is covered separately here: Move emails and folders between accounts
Duplicate Issues: