I do not use Time Machine, SmartGuard or any kind of backup except for som usb flash drives. After I assured I had nothing left in the Recycle Bin in Windows 11 I made a little test for Parallels 19.4.1: My free space was 402 Gb and then I deleted a file with the size 5 Gb. Once again I assured my Recycle Bin was empty so my free space now ought to be 402 Gb - 5 Gb = 397 GB. But the storage remain on 402 Gb! Why do I not get 5 Gb more free space? No wonder why my free space through a couple of month have decreased so fast. In that way the splendid Parallel becomes useless, because you cannot add big files to your system when it's impossible to regain free space after removing them again.
It sounds like the space inside your Parallels VM isn't syncing up properly with your Mac's free storage. This can happen because Parallels doesn't always immediately shrink the virtual disk file when you delete stuff in Windows. One thing you can try is using the "Reclaim Disk Space" feature. Open Parallels, go to the Control Center, click on your VM, and you should find an option like "Free Up Disk Space" in the settings. That should free up some of the unused space and get things back on track. Also, check if there are any snapshots stored in the VM settings--they can take up a surprising amount of space if you don't clean them up regularly. And if you haven't already, enabling "Optimize Storage" might help manage this better in the future.
