CustomString is designed to allow ull customization. or example, you can map you local to a speciic name. Normally es-BO is mapped to Español (Bolivia), but using this CustomString you can map your locales as es-BO:Castellano (Mauricio)
You can also use the other tags there. es-BO: Castellano ([TwoLetteISOCODE])
hose mapping are set in the advanced behavior page.
I am taking some time to update the list of tags and including ome somple videos.