Navigating IMAP folders?

[Paul Gilmartin]

Hello, Mutt,

I have a fairly complex tree of folders on an IMAP server.  So:

o Some of my folders contain both messages and subfolders.  When
  I focus on such a folder, <Return> shows me subfolders, not
  messages.  How can I view the message list, instead/also?
  (I thought I knew this, long ago, but "?" shows me no such
  command.)

o How can I navigate to the parent of a displayed subfolder.
  Sometimes I see a "../" entry which does this.  Why not
  always?

I choose to leave everything on the server to be accessible
on multiple devices with various clients.

Thanks,
gil