In Xcode 10, the toolbar had an inter-locking ring icon which showed the assistant editor, it\'s missing in Xcode 11.
In Xcode 11 we now have multiple editor panes. You can summon a second pane, a third pane, as many as you like.
When you have a second pane, it does not have to be an automatic assistant. In other words, the editor pane itself either is an assistant or it is not. So if it is not, it is manual. And if it is, it is automatic.
To toggle between being an assistant and being an ordinary pane, choose Assistant from the Editor menu:
If Assistant is checked, this is an assistant and is automatic. What it displays depends automatically on some other pane.
If Assistant is unchecked, this is an ordinary editor pane and is manual. You can display anything you like in this editor.