There's no harm at all in moving the unallocated space, assuming of course, that your partitions are healthy and have no existing issues (GParted would check for this anyways).
If you want to resize your btrfs partition you can save a step by moving the unallocated space to the slot before the btrfs partition and then reisize the btrfs partition, but it wouldn't make much of a difference anyways because the btrfs partition would need to be moved left regardless.
Btw, questions like these are best posted to a Linux community, like [email protected]