I have 2 drives in my Windows 10 machine. Windows sits on an SSD, and I've got a much larger rotational drive. Generally speaking, Windows recognizes the rotational drive just fine, and I've moved some default folders over to it. It does let me change the drive for photos and music, for example.

But I can't get it to install apps to it. It's just disabled. Same goes for the option to move apps - that's disabled, while uninstall is available:
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Anybody know how I can get Windows to let me install apps to my D: by default?