I started a solo walk and now want to transfer my the steps I've spent on it to my new group walk. How do I do that?

You can't do that but there is an easy way to sort this out. Just delete your solo walk. This will return the steps you spent on it to your bank. You can then respend them on your group walk.

Here is a link to another article in our Help Section which explains how to delete your walk: https://worldwalking.org/help/article/9662/deleting-or-leaving-a-walk