Is there an invitation to a conference on Asterisk via buttons?

Question

Asterisk

A simple conference is configured via sip.conf:

[local]
exten => 900,1,Answer()
exten => 900,n,Macro(recording,${CALLERID(num)},${EXTEN})
exten => 900,n,ConfBridge(1,confer)

and confbridge.conf

[confer]
type=bridge
max_members=20
video_mode=none
mixing_interval=10
internal_sample_rate=auto
record_conference=no

those. people enter the conference themselves or they are translated by the secretary. And how to invite people to the conference while in it?
2-3 people in the room communicate and you need to call more, how to do this? I did not find a keyboard shortcut or setting where this can be done, including in features.conf

Answer 1

confbridge.conf

[admin_menu]
...
*#=dialplan_exec(conf-invite,s,1)

extensions.conf

[conf-invite]
exten => s,1,Answer
same => n,Read(NUMBER,vm-enter-num-to-call)
same => n,Originate(SIP/${NUMBER},exten,conf-invite,conference,1)

exten => conference,1,Answer
same => n,ConfBridge(conference,bridge,simple-user,user_menu)