Unable to understand the instructions for building a symlink
Depending on the version of macOS you're running, the temporary files for a screen recording may be stored in different locations by default.

Later macOS use screencapture and the temporary recordings are stored in ~/Library/ScreenRecordings.
Earlier macOS use QuickTime and the temporary recordings are stored in ~/Library/Containers/com.apple.QuickTimePlayerX/Data/Library/Autosave\ Information.

In the following commands, replace /path/to/recordings with one of the above paths depending on your version of macOS. You can also safely run each command twice with each of the paths above to symlink both folders to the same destination.


Delete the existing folder to be able to create the symlink in its place.
rm -rf /path/to/recordings


Create the symlink.
ln -s /path/to/destination /path/to/recordings

where /path/to/destination is the path to the folder you want the temporary recordings saved to instead of their normal location. See How can I create a symbolic link in Terminal?.