is it possible to add a custom special use mailbox

[Marc]

Currently I am using this to try and catch everything in Sent. 

  mailbox Sent {
    special_use = \Sent
    auto = create
  }
  mailbox "Sent Items" {
    special_use = \Sent
    auto = no
  }
  mailbox "Sent Messages" {
    special_use = \Sent
    auto = no
  }

I would like to have something

  mailbox Test {
    special_use = \Test
    auto = create
  }
  mailbox "Test Items" {
    special_use = \Test
    auto = no
  }
  mailbox "testing" {
    special_use = \Test
    auto = no
  }