How Do I Grant RDS FullAccess Permissions to a Sub-user?
RDS FullAccess is a region-level permission. You need to assign permissions for region-specific projects.
RDS is a project-level service deployed and accessed in specific physical regions. To assign RDS permissions to a user group, specify the scope as region-specific projects and select projects for the permissions to take effect. If All projects is selected, the permissions will take effect for the user group in all region-specific projects. When accessing RDS, switch to a region where you have been authorized to use RDS.