Accessing other user resources with management account

As the management account owner, you won't be able to directly access resources created by other accounts within the organization by default. Each account in an AWS Organization is a separate entity, and resources created within those accounts are isolated for security reasons.

To access resources created by other accounts in your organization, you can do the following:

Cross-account access: You can create a cross-account IAM role in the member account that allows access to specific resources. Then, you can assume that role from your management account to access the resources in the member account. This is the recommended approach for accessing resources across accounts within an organization. Here is a brief outline of the process:

a. In the member account, create an IAM role that allows cross-account access, with the management account ID as a trusted entity.

b. Attach policies to the role that grant permissions to the resources you want to access.

c. In the management account, create an IAM user or role with the permission to assume the cross-account role.

d. Use the AWS CLI or SDK to assume the cross-account role and obtain temporary security credentials.

e. Use those temporary security credentials to access the resources in the member account.

For a detailed guide on setting up cross-account access, please refer to the AWS documentation: Tutorial: Delegate Access Across AWS Accounts Using IAM Roles

Resource sharing: In some cases, you can share resources across accounts using AWS Resource Access Manager (RAM) or specific service sharing features. For example, you can share Amazon RDS, Amazon S3, and VPC subnets across accounts. Note that this method is limited to specific services and resources, and it doesn't provide the same level of flexibility as cross-account access with IAM roles.

for more information

https://docs.aws.amazon.com/organizations/latest/userguide/orgs_manage_share.html