I thought I read/heard something about "shared" WebMap access somewhere? Rather than changing ownership of a WebMap, I want two people to be able to maintain it. Is this possible?
Yes you can do this with web maps and web scenes. As the admin of the org you can create groups that allow shared ownership of items in these groups. The creator stays the owner but other members of the groups can push changes to the original item.
Share items—ArcGIS Online Help | ArcGIS
Check out the link below...I think you will find your answer. You can create a group and allow all group members the ability to update items shared with that group.
"Share" Web Map Application (Story Map) for Editing
Retrieving data ...