You linker error actually goes thru to UMG module it self as it can not resolve links that are referenced in UMG module. I don’t know if this gonna fix the issue but i notice other issue in your code, this:
UPROPERTY()
UUserWidget* createdWidget = nullptr;
UPROPERTY as any other U macros only works in UObjects and only UObject classes getting reflected so it useless. But this also rises other issue, engine won’t see your UUserWidget* reference, which means whatever you create and refrence only here is a subject of garbage cleaning. You can prevent that you need to set flag to the UObject SetFlags(RF_MarkAsRootSet), remeber that this won’t be GC so everything oyu will refrence there never gonna be colelcted too so watch out what you doing there or lese oyu might get yourself to seriues memory leak issues, it is best to find some UObject in editor features to host it instead
For UObjects outside of UObject classes you should also use special pointer TWeakObjectPtr which save you form any invalid pointer issues
Also UMG and blueprint in general was not made to work in editor-time, UMG was made to work on gameplay viewport so there high chances that what you trying to do won’t work. TakeWidget() will get you widget data but scripting for them that sit in blueprints won’t work.