This post is from a low-reputation account and contains an unverified outbound link. Be cautious before clicking external links.
For such Synergy KVM Environments as in,
Windows PC <-> MAC PC
I tried several ways such as tweaking in the registry of Windows OS (set on mouseflip), but none worked but this !
"WizMouse Portable"
Just download it from the website,
https://wizmouse.en.lo4d.com/
This will solve everything !