In the latest build, new feature has been added to the Unattended page, the ‘Disk partition configuration’.

It goes without saying, be very careful using this feature.
Depending on what you select, it can wipe your disk clean, create and format partitions, and install Windows to a partition without user interaction.
Let me highlight it again, these options can erase your disk by simply booting the image if you set it up to do so.
Of course people who requested such a feature will welcome it, as it speeds up deployment.

A lot of work went into the implementation, to be simple as a few clicks to setup while magic happens in the background, so it is for licensed users only.

Enjoy, and be careful.