How can you narrow your topic to a single spoke or to a sub-header of a spoke on the map?

The answers that you find on the following site may be of help to you. I hope that they are.

single spoke and sub header spoke - UsingEnglish.com ESL Forum

By your asking the question. I have just learned something about what you are asking. I learned something new. I did not know anything about "spokes" or "maps" as related to writing.

Just another link that may be of use to you.

https://www.askmehelpdesk.com/advice/t-47074.html