Excellent piece of work, I have been chasing this problem for days, it is good that you have pulled it all together. Your post relates to UE4.24
My reply relates to UE4.23 (Magic Leap version), the paths differ. UE4.23 wants to install to C:\UE4 due to a problem with maximum path length
The 4 paths you listed were:
D:\Program Files\Epic Games\UE_4.24\Engine\Plugins\2D\Paper2D\Source\Paper2D\Classes
D:\Program Files\Epic Games\UE_4.24\Engine\Plugins\2D\Paper2D\Source\Paper2D\Intermediate\Build\Win64\UE4Editor\Inc\Paper2D
D:\Program Files\Epic Games\UE_4.24\Engine\Plugins\2D\Paper2D\Intermediate\Build\Win64\UE4Editor\Inc\Paper2D
D:\Program Files\Epic Games\UE_4.24\Engine\Plugins\2D\Paper2D\Source\Paper2D\Public
The UE4.23 equivalents are:
C:\UE4\MagicLeapUE4Editor\Engine\Plugins\2D\Paper2D\Source\Paper2D\Classes
Not found
C:\UE4\MagicLeapUE4Editor\Engine\Plugins\2D\Paper2D\Intermediate\Build\Win64\UE4Editor\Inc\Paper2D
C:\UE4\MagicLeapUE4Editor\Engine\Plugins\2D\Paper2D\Source\Paper2D\Public
I cannot find a path that matches, your second path.
In UE4.23 the definitions need to be placed under Project->Properties->NMAKE->Preprocess Definitions (Preprocessor not Processor as per original post)