For all the people who need a solution for this problem. The solution is more or less straight forward, you just have to do it manuially, on OS level,, and not the GUI.
Steps to do:
1) Create a empty VM (the cloned one) by copying and editing the <VM-ID>.conf file of the parent VM. (/etc/pve/nodes/<host>/qemu-server/<parent VM-IS>.conf).
2) clone the parent-snapshot: zfs clone rpool/data/vm-<parent VM-ID>-disk-0@<snapshot> rpool/data/vm-<cloned VM-ID>-disk-0
i#m writing a script that automaticlly does all the checks (target ID not used, set new strorage, new MAC in cloned-VM.conf file) and do the clone. If i finished i will publish it here / in GitHub.