When I set Cyberduck to a maximum limit of one transfer, I would normally expect to start one transfer and then be able to queue up additional transfers which would wait until the first transfer is finished. However, what I see is that initiating a second transfer actually starts the transfer instead of waiting.

In other words, setting the transfer limit to 1, always allows 2 transfers. Additional transfers after two will always wait as expected. Basically there is no way to have only one transfer and to queue the rest at the same time.