I've been attempting to mod W2 with the Nexus Mod Manager but it says I'm missing "The Witcher 2 Enhanced Edition\bin\userContentManager.exe".

I've tried installing several times but no luck. Anyone know the issue here?

If you haven't already, I would contact GOG's support staff about the issue.

Part of patch 3.4. If you have an older game and it's not patched up to 3.4, you need to install this before installing mods.

If you downloaded from GOG recently, you have patch 3.4 and this file already. If you have an older download, let the Launcher run and apply patches for you.