Ability to change a subnet into a supernet

Change/edit an existing subnet and convert it into a supernet.  Ex. If I have already an existing /24 subnet and I wanted to break it down into smaller /27 subnets. I will not be able to unless I delete the subnet, recreate it into a /24 supernet and hen I can create smaller /27 subnet.  This is too much work, edit field would do the trick if possible.