Take a look at this article: Ask Ars: “My SSD does garbage collection, so I don’t need TRIM… right?” | Ars Technica. Every other function should be self-contained.'

All it should require is the data to write and the data to retrieve. You may also reclaim available disk space manually by following instructions from KB114654.'A drive should not have to be told how to take care of itself. Once Windows triggers TRIM for its disks, Parallels Desktop detects it and resizes *.hdd accordingly.In the opened window you may run optimization manually (1), and configure disk optimization frequency (2): (In Windows 7 VM this window is called Disk Defragmenter)

In Windows 8.1 or 10 VM click on Start button > type Optimize Drives > select Defragment and Optimize Drives.

Go to Options > Optimization > check the Free Space: Real-time virtual disk optimization option. NOTE: Real-time virtual disk optimization may affect a virtual machine's performance while doing the compacting (not constantly). Go to Hardware > Hard Disk 1 > check the Free Space: Real-time virtual disk optimization option. In this case, the option to enable TRIM will not be presented in the configuration window of the virtual machine because for NVMe disks TRIM should be always working, due to the design of the driver. Note: Parallels Desktop 15 provides you the ability to create virtual machines with NVMe virtual hard drives. Go to Hardware > Hard Disk 1 > unwrap Advanced Settings > check the Enable TRIM option.

To enable the real-time optimization on the traditional HDD drive you need to shut down your VM -> open your virtual machine's configuration. This feature is enabled by default if your Mac's primary hard drive is an SSD drive, and it is available for Windows 7, 8, 8.1 and 10 virtual machines and the OS X virtual machines starting from 10.8 Mountain Lion. But you can also optimize drives on your PC manually.

The real-time disk optimization feature relies on a TRIM command, which is used in Windows by Optimize Drives option (previously called Disk Defragmenter), and by default runs automatically on a weekly schedule. We have created a feature that takes care of that for you. Since Parallels Desktop version 10 you no longer need to think about the unused disk space in your Windows virtual machine (VM).

Force enable trim mac os