How do I rebind the keys in the attachment prompt?

[lists at ifohancroft.com]

Hi,

I am totally lost about this:

When you are on the compose screen and you hit 'a' (attach-file) you get 
an attachment prompt, that says:
Attach file ('?' for list):

There you have 3 options (that's how many I found):
1. Hit ? and you get a list of your mailbox folders
2. Hit Tab and you get the browser showing your local files (and you can 
select an attachment from there
3. Just type the path to an attachment (and you can use Tab to 
autocomplete the name).

How do I rebind the keys for this prompt? Like setting a key to hit 
instead of Tab to show the file browser or remapping the action that 
currently is bound to ? to something else. I went through Mutt's manual 
multiple times and couldn't find anything about it.

Is there a help screen for this prompt? How do you open it?

Also, is there a setting I can configure so when I hit ? for 'list' I 
get the file browser as opposed to the mailboxes.

Best Regards,
IFo Hancroft