is it possible to add a custom special use mailbox

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 }