Mouse clicks on the debug menu are offset incorrectly while in windowed mode. It see for yourself just hit ALT + Enter to go into windowed mode, hit the maximize button to see the debug menu and try to hover over an element with your mouse.

This is actually true in Fullscreen as well on my machine, where I have the desktop height set to 1050px (native size for my LCD)

I haven't had time to investigate/debug it.

I believe this is the Unproject() calculation, if you enable the debugCamera at a different DistanceAboveTarget (ex. 25.0f)in the GetRenderEntityBasisP function, your mouse will now need to be at the top of your screen (same place as if the debugCamera was off) to highlight/click on the trees that are almost in the middle of your window/screen now.