I’d really lile to see this feature as well. 
Both yes and no, right? If you’re on a POP-account, then yes - but, if on an IMAP-account it would sync right up.
The issue I have right now, as new/more emails are dropping in - I need to go online to the webmail, create the folders, then go back into the app, and refresh the folder list. Then I can start sorting my emails.
If it’s a POP-accoumt (downloading all)… Of course I’d like to be able to sort my emails into folders. No one likes a crowded inbox. I know I don’t. 
I thing I’ve noticed… When creating a subfolder online, and syncing it back. The subfolder shows up as its own, but with the name pattern:
- foldername
- foldernam.subfoldername
I guess it’s ok’ish. But one of the benefits to create subfolders are to reduce the lenght of the list with folders.