Abiquo 4.5 includes a new action to resize a disk as part of an action plan. You just need to select the disk, and supply the amount of disk space to add, and the units. You will need an appropriate VM template to use this feature. The platform will only increase the size of the disk; it will not perform other actions such as modifying the disk partitions.
For more details of how to use the Action plans feature for VM automation, see Manage Action Plans. For more details of how to work with cloud automation, see Control View - Alerts and Control View - Cloud Bursting