I reproduced a problem with delete and undo of macros
(and even got/reported same crash mentioned here ^^ :
Crash opening a BP containing a deleted CustomMacro - Platform & Builds - Epic Developer Community Forums)
- I created a macro in an macro library, added it into an actor blueprint.
- Saved and compiled.
- Deleted macro and did an UNDO - saved
- BPs where this macro is added causing this error when saving:
Can’t save …/…/…/…/…/…/UnrealEngine/Test/Content/Test/NewBlueprint.uasset: Graph is linked to private object(s) in an external package.
External Object(s):
NewMacro_0
If i get this error due to modified or just saved C++ functions that I am using for Blueprints, i just refresh BP nodes.
But this did not work. Refreshing nodes of macro BP graph did not work as well.
So what i tried next:
- Deleting Macro Node in BP, compile, save, add it back again. Save failed.
- A Duplicated Macro in Library causes same issue, even when whole Macro Library is duplicated.
Recreating Macro worked around Crash-Issue and it works here as well but can cause a crash too^^.
- NewMacroLibary (Actor), NewBlueprint (Actor) with NewMacro_0 added. - save, compile, both windows still open.
- Delete/Undo Macro
- Save NewBlueprint fails
- Delete and create (save) NewMacro_0. Compiling of BP causes Editor Crash.
- Problem gone - after opening editor of course.
In my project I accidentally deleted macro when failing to mark a reroute node. I am not surprised that an undo can cause issues and maybe those issues are already fixed. But a delete confirmation message when macro is in use, would be nice 
I created a new macro and copied graph and deleted few macro nodes in de BPs (therefore I had no crash at all)