VM VirtualBox convert fixed disk to dynamic

C:\Program Files\Oracle\VirtualBox>VBoxManage.exe clonemedium disk "C:\Users\zchen\VirtualBox VMs\EnviMachine\EnviMachine.vdi" "C:\Users\zchen\VirtualBox VMs\EnviMachine\Envi-ARCGIS-Machine.vdi" --variant Standard

0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...100%

Clone medium created in format 'VDI'. UUID: 802a3626-cb39-4b76-a3dc-d320dab59353

reference:

https://www.howtogeek.com/312456/how-to-convert-between-fixed-and-dynamic-disks-in-virtualbox/