@DatagroupUser: There's no specific version that suddenly made WinSCP compatible with Windows 10.
You can run almost any version of WinSCP on Windows 10.
Having that said, always use the latest version of WinSCP!
Version 5.9.1 added the following capability for Windows 10:
Make WinSCP default handler command opens Set Program Associations for WinSCP even on Windows 10.
The release notes show this at: https://winscp.net/eng/docs/history?a=5.9.1