The “Text conference” is not completely removed. The idea is that most of the conference conversations to be shifted to the new feature “Chat Rooms”.
Chat Rooms allow more control and are easier to monitor who and what messages have sent. Chat Rooms stay and can be reused when people Sign Out and then Sign In.
If you have groups in your contacts list, you can select a group. Then click on the “Chat” button on the toolbar on the right. This will open the old-style conference with all online group members. From its window you can add more participants to this Text Conference.