! DANGER you can mess up your PC with this!
If you have trouble with C:\ free space, you can easily migrate your Frontier_developments folder to another drive, using this guide. Follow it step by step, and you're done.
If you are not sure what you are doing, ask for help or find another method, this can ruin your installation or worse. For me, it worked just fine. Actually it is a pretty simple, primitive 'link' for your windows to know where to find your new Fdev folder (Elite). Use at your own risk, any typo can be a problem. I didn't migrate all my appdata folder, that for sure would have consequences at the next Windows update, so I just moved the Frontier_Developments folder. I have NON-steam version, no idea about that.
If you need to change the location of your ShareGate Desktop application data, you can use mklink in the Windows Command Prompt to create a symbolic link with the following steps: Close ShareGate ...
support-desktop.sharegate.com