-Hmm... Is it not in the post editor you get for 15 minutes after a post? I'll look into that.-
You can also change your Current Location while you're not posting by editing your profile
EDIT – If you forget to put in your location, you have 15 minutes to edit your last post, so just click the Pencil and then you change your Location as well as fix any mistakes in your post (like I've just done)...
