Mail folders are driving me nuts!

I have IMAP access setup for my GMail accounts within Mail.

How can I create (sub)folders (I guess they are called mailboxes in Mail) that will appear under my Inbox? Currently if I create additional mailboxes, they appear outside my Inbox as a separate item in the sidebar.

Here's the layout that I am seeking:

Code:

- Mailboxes
  - Inbox
    - Gmail Account 1
       - Folders
       - Folders
    - Gmail Account 2
       - Folders
          - Subfolders
       - Folders
       - etc.

Currently, if I create mailboxes/folders this is what I get:

Code:

- Mailboxes
  - Inbox
    - Gmail Account 1
    - Gmail Account 2

- Gmail Account 1
  - Folder
  - Folder
- Gmail Account 2
  - Folder
  - Folder

This is annoying since my inbox becomes separated from my folder structure.

By the way, I have my IMAP prefix set to INBOX (in order to avoid duplicating the emails under GMail's 'All Mail' label). Changing it to nothing doesn't seem to help anyway.