In version 20 you will need to select "System Extension", not "Extension"
View attachment 45397
If you select this and you cannot see your queue(s)
View attachment 45398
then you need to go into your options of the system and allow the viewing of system extensions
View attachment 45399
Just remove the highlighted option and your queues will be visible now.
Founded in 2005, when VoIP was an emerging technology, 3CX has gone on to establish itself as a global leader in business communications.