You have already begun using VCF Automation 9.x with the All Apps setup, but want to switch to using the VM Apps management
VCF Automation 9.x
If you have already begun using VCF Automation, then you need to remove all resources under the organization. Once that is complete, remove the existing supervisor. From here, you should be able to create the necessary cloud account and switch to using VM Apps.
Disable supervisor
https://techdocs.broadcom.com/us/en/vmware-cis/vcf/vcf-9-0-and-later/9-0/vsphere-supervisor-installation-and-configuration/updating-vsphere-supervisor/managing-a-supervisor-cluster-using-vlcm/disable-a-supervisor-cluster.html