Just need a little correction at this line:
class FTimeline DoorTimeLine;
For parser it means that it is actually class, if there’s no “class” or “struct” keywords, so this is common type (float, int, char etc.).
.h don’t have header included for FTimeline, so it knows that it is a type (UnrealParser knows), but don’t know what behind this type.
And don’t forget to include header for FTimeline in .cpp (not in .h), this will be something like “GameFramework/Timeline.h”.