Custom editor notifications

Use FNotificationInfo with FSlateNotificationManager::Get().AddNotification(Info); Then use SetCompletionState to set the status (success, fail, …).

Snippet example (thanks to Hojo, Unreal Source Discord)

void PostNotificationInfo_Warning(FText Title, FText Description, float Duration)
{
	FNotificationInfo NotificationInfo(Title);
	NotificationInfo.ExpireDuration = Duration;
	NotificationInfo.Image = FAppStyle::GetBrush("Icons.WarningWithColor");
	NotificationInfo.SubText = Description;
	FSlateNotificationManager::Get().AddNotification(NotificationInfo);
}

To use FAppStyle you need to include SlateCore module.

You can find another simple example at UMassEntityConfigAsset::ValidateEntityConfig