Sorry, forgot more. The idea is that you have 1 dictionary of gameplay tags (added/imported like above). Somewhere in your game code on startup, you need to tell the GameplayTags system. Something like this:
IGameplayTagsModule& GameplayTagsModule = IGameplayTagsModule::Get();
GameplayTagsModule.GetGameplayTagsManager().LoadGameplayTagTable(GameplayTagTableName);
This needs to be done at editor startup too… so the correct way is to make a UEngine subclass for your game. But that is a lot of steps. It is probably easiest to stick the above line somewhere in UEngine::Init.