Trying to Merge Child-Root account to Root (Management) Account

In our organization hierarchy we have our Root account (Management Account) and a child root-account. I want to be able to merge or move everything from the child root-account to the Root Management Account. When I try to move the account, I get duplicate account error.

The issue is the Management Account cannot see the resources being deployed on the child root-account such as S3 Buckets.

Is there a policy I can create that will allow the Management Account to see the resources or is there a way for me to move all resources from the child root-account to the Root Manager Account?

Also, would like to delete the child root-account. When you log into Organization and you look at root, you have the management account and then other accounts that can be signed into as root user.