Is there something similar for Windows that will use the Windows Credential Manager (or something like that)?
not that I know of, but note that the regular pinentries on Windows can cache the private key as long as you want. (Almost all pinentry can do this.) So you would enter the passphrase only once for your caching time. If you set the caching time to a full work day, you’d only enter it once.
Hard to say. I do not know enough about the Windows Credential Manager to say how useful it would be. Especially how easy it would be to integrate technical and what the security implementation are.
So a good path could be to try to implement it as Free Software and then see if it can be integrated officially.