Once a caller is in a queue there is no possibility of the caller to press a key to leave the queue. You can set an EWT, or define a level (1 to 5) to route the call to an IAA or IVR. As you specified IAA, i’ll talk about that. Once the call is “transfered” to the IAA, you can present the caller to leave a message (transfer to voice mail) or return to the queue. Therefore answers to your questions:
what kind of leaf do I have to use and what number to dial to return to the queue:You can have both options in 1 AA leaf (Menu for Auto Attendant).
Option 1 (DTMF digit) routes to a forwarded extension or direct to the voice mail for the pilot receiving the call.
Time out action – Release. This will take you back to the queue without losing your position in queue.