If you don't need a virtual machine any more, you can permanently remove it from your Mac:
Warning: Before removing, check that none of the virtual machine files (e.g. virtual hard drives) are used by other virtual machines. If you remove a Boot Camp virtual machine, the Boot Camp partition with Windows installed remains available on your Mac.
Shut down the virtual machine if it is running, right-click in the virtual machine window and choose Remove. You can also click File > Remove or right-click this virtual machine in the Control Center and choose Remove.
Click Move to Trash.
To temporarily remove a virtual machine from Control Center:
Shut down the virtual machine if it is running, right-click in the virtual machine window and choose Remove. You can also click File > Remove or right-click this virtual machine in the Control Center and choose Remove.
Click Keep Files.
When you need this virtual machine again, you can easily import it in Parallels Desktop.