The name generated by the UI is sometimes invalid (too long). If user will provide custom disk name longer then 20 chars the generated name will always be invalid.

4.20

Custom name: always
Generated name: 20% (?)

1. add a new disk using "Add Empty disk(blank)" modal
2. disk name is generated for the user (but editable) - make sure it's longer then 20chars
3. create the disk my clicking "save"  
4. detach the disk (action in the kebab menu)
5. add volume again using virtctl i.e. :=
» virtctl addvolume centos-stream9-bronze-termite-38 --volume-name=dv-centos-stream9-bronze-termite-38-disk-black-scorpion-97-8xjlop -n radek --persist

error adding volume, admission webhook "kubevirt-crd-status-validator.kubevirt.io" denied the request: must be no more than 63 characters

volume is successfully added