since LuaPlayer.map_view_settings is not readable, it unfortunately isn't possible to guard adding a tag based on tag visibility.
But, it is possible to make tags visible as soon as the player adds one, by just setting LuaPlayer.map_view_settings = {["show-tags"]=true}.
To make the user experience with that even better, it would also be nice if it automatically turned it back off if the user closes the GUI without actually adding a tag. this should be reasonably easy to do since you already have your own GUI.