When running Hassio in a virtual machine, it is, to my knowledge impossible to extend the storage. It is possible to.increase the disk size with vboxmanager but in Hassio you can’t format the additional space.
A gparted tool would be handy in this case in Hassio. Either through SSH or perhaps even through an add on.
Hassio stores its data outside its docker containers in the underlying operating system.
Do you mean HassOs or do you have Hassio installed on another OS?
And why gparted? HassOs is strictly command line. parted could make more sense.
Or you could just as easily boot to a live distro of gparted or Ubuntu and expand the partitions to your desired size.
Hassio installed as virtual machine. Resizing disk size is a crime this way.
So that would be HassOs.
Adding a graphical desktop environment just for graphical disk resizing would be a crime