How to map the Windows key to option in Microsoft Remote Desktop version 8

By default, Mac OS uses VNC combined with a few extras (e.g. auto-discovery via Bonjour) when you use Screen Sharing, and in most cases this is all an average user needs. For system administrators however, there is usually a need for more control over the computers they support; therefore Apple provides "Apple Remote Desktop" (ARD) which offers a lot more control mechanisms (like terminal sessions, remote installation of software, remote shutdown, remote execution of automator scripts) and this is possible with groups of many computers at the same time. For this feature to work, SSH and remote management needs to be activated.

So in short: Screen Sharing is roughly equivalent to VNC, while Apple Remote Desktop is a "high-end" remote administration software which requires "Remote Management" to be turned on. There is also a difference in how incoming screen sharing requests are handled: with "Screen Sharing" enabled, if an observer connects with a user account that's different than the one currently logged in and clicks Share Display, the user needs to confirm before the screen is shared. With "Remote Management", the screen is immediately shared without a prompt appearing.

The easiest way might be to disable the Fn key. Since you say that using Fn+F10 works, you could go into System Preferences > Keyboard > Keyboard, and enable Use all F1, F2, etc. keys as standard function keys. This way you no longer need to press Fn to send F10.

The second solution is on the PC side. You could install a utility such as AutoHotkey on your PC and remap the keys there. That way the keybindings will only work on the PC. Lifehacker has nice looking tutorial about this. In AutoHotkey, you can decide which applications the shortcut applies to, but in your case it seems like a global hotkey would work since it is running on the PC side.

Another solution might be to try one of the ways to create keyboard shortcuts menitoned in this Lifehacker article. This article's goal is to help you do similar things that AutoHotkey let's you do on the Mac.