Great question — answering as the UphillTech team:
You should move your Linux partition with the help of LiveUSB boot up or one of Windows partitioning tools. While you are actively using Linux, I don't think you can move the partition safely. That is if you want to add the unallocated space to Linux partition of course.
Full answer by Arya Volkan Şen: https://askubuntu.stackexchange.com/a/717223 (CC BY-SA 3.0).
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