With further digging, the issue appears to persist regardless of whether I use an enum or name variable.
Of interest is that when using the name variable, the editor only crashes when re-launching instead of when merely saving/compiling the parent widget.
Below i the callstack.
UnrealEditor-UMG.dll!UUserWidget::GetExtension(TSubclassOf<UUserWidgetExtension> InExtensionType) Line 2261 C++
[Inline Frame] UnrealEditor-UMG.dll!UUserWidget::GetExtension() Line 1154 C++
UnrealEditor-UMG.dll!UE::UMG::Private::FindOrAddWidgetNotifyExtension(UWidget * Widget) Line 1850 C++
UnrealEditor-UMG.dll!UWidget::K2_AddFieldValueChangedDelegate(FFieldNotificationId InFieldId, FFieldValueChangedDynamicDelegate InDelegate) Line 1917 C++
UnrealEditor-UMG.dll!UWidget::execK2_AddFieldValueChangedDelegate(UObject * Context, FFrame & Stack, void * const Z_Param__Result) Line 981 C++
UnrealEditor-CoreUObject.dll!UFunction::Invoke(UObject * Obj, FFrame & Stack, void * const Z_Param__Result) Line 6665 C++
UnrealEditor-CoreUObject.dll!UObject::CallFunction(FFrame & Stack, void * const Z_Param__Result, UFunction * Function) Line 1139 C++
[Inline Frame] UnrealEditor-CoreUObject.dll!FFrame::Step(UObject *) Line 477 C++
UnrealEditor-CoreUObject.dll!ProcessLocalScriptFunction(UObject * Context, FFrame & Stack, void * const Z_Param__Result) Line 1209 C++
UnrealEditor-CoreUObject.dll!ProcessScriptFunction<void (__cdecl*)(UObject *,FFrame &,void *)>(UObject * Context, UFunction * Function, FFrame & Stack, void * const Z_Param__Result, void(*)(UObject *, FFrame &, void *) ExecFtor) Line 1039 C++
UnrealEditor-CoreUObject.dll!ProcessLocalFunction(UObject * Context, UFunction * Fn, FFrame & Stack, void * const Z_Param__Result) Line 1279 C++
[Inline Frame] UnrealEditor-CoreUObject.dll!FFrame::Step(UObject *) Line 477 C++
UnrealEditor-CoreUObject.dll!ProcessLocalScriptFunction(UObject * Context, FFrame & Stack, void * const Z_Param__Result) Line 1209 C++
UnrealEditor-CoreUObject.dll!UObject::ProcessInternal(UObject * Context, FFrame & Stack, void * const Z_Param__Result) Line 1306 C++
UnrealEditor-CoreUObject.dll!ProcessScriptFunction<void (__cdecl*)(UObject *,FFrame &,void *)>(UObject * Context, UFunction * Function, FFrame & Stack, void * const Z_Param__Result, void(*)(UObject *, FFrame &, void *) ExecFtor) Line 1039 C++
UnrealEditor-CoreUObject.dll!UObject::CallFunction(FFrame & Stack, void * const Z_Param__Result, UFunction * Function) Line 1149 C++
[Inline Frame] UnrealEditor-CoreUObject.dll!FFrame::Step(UObject *) Line 477 C++
UnrealEditor-CoreUObject.dll!ProcessLocalScriptFunction(UObject * Context, FFrame & Stack, void * const Z_Param__Result) Line 1209 C++
UnrealEditor-CoreUObject.dll!ProcessScriptFunction<void (__cdecl*)(UObject *,FFrame &,void *)>(UObject * Context, UFunction * Function, FFrame & Stack, void * const Z_Param__Result, void(*)(UObject *, FFrame &, void *) ExecFtor) Line 1039 C++
UnrealEditor-CoreUObject.dll!ProcessLocalFunction(UObject * Context, UFunction * Fn, FFrame & Stack, void * const Z_Param__Result) Line 1279 C++
[Inline Frame] UnrealEditor-CoreUObject.dll!FFrame::Step(UObject *) Line 477 C++
UnrealEditor-CoreUObject.dll!ProcessLocalScriptFunction(UObject * Context, FFrame & Stack, void * const Z_Param__Result) Line 1209 C++
UnrealEditor-CoreUObject.dll!UObject::ProcessInternal(UObject * Context, FFrame & Stack, void * const Z_Param__Result) Line 1306 C++
UnrealEditor-CoreUObject.dll!UFunction::Invoke(UObject * Obj, FFrame & Stack, void * const Z_Param__Result) Line 6665 C++
UnrealEditor-CoreUObject.dll!UObject::ProcessEvent(UFunction * Function, void * Parms) Line 2145 C++
[Inline Frame] UnrealEditor-UMG.dll!UUserWidget::PreConstruct(bool) Line 1735 C++