Know limitation of UnrealHEaderTool. Everything inside of any #ifdef except WITH_EDITOR and WITH_EDITORONLY_DATA will be ignored by UHT.
#ifdef and #ifndef have no affect when used in the header file of a class.
ANumber variable does not show up in the editor when MYMACRO is not defined. Inverse also does not appear in editor (using #ifdef with macro defined)
ANumber does not appear in the details panel for the MyActorBP instance
Head over to the existing Questions & Answers thread and let us know what's up.