It's really a shame, that VHDX support has been dropped!
It was always very practical to use such discs either because they were intended for "the competitor" or because they were created with Disk2vhd for example.
After the company changes/restructuring and thus uncertain future prospects in 2016, things have calmed down again.
But just dropping such a feature... doesn't make you feel good about the future of VMware Workstation.
Greetings,
Martin