You can use any geometric shape for these new areas, or sketch a small picture to represent them better for the right side of your brain. Ask yourself who, what, why, where, when, and how. This will help you in finding topics and sub-topics. Think fast . . . Use different colored pens or pencils to designate related topics.
Symbols can be very valuable, as well.
Mindmaps work to a great degree because of your choice of keywords. Don't elaborate for any of these topics. Instead, use a keyword or two. It will mean so much more to you than a complicated sentence. It is easy to over-verbalize a mindmap.