I'm glad we have this thread.
Is there a need/desire for region-specific translation files for Spanish? According to one list, Spanish is the official language in at least these countries:
Argentina, Bolivia, Chile, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, Equatorial Guinea, El Salvador, Guatemala, Honduras, México, Nicaragua, Panamá, Paraguay, Perú, Puerto Rico, Spain, Uruguay, and Venezuela.
Granted, ToDoList is probably not used in All of these countries. And, it's up to individuals who speak a dialect to do their own translation.
But is it reasonable, for example to copy/paste "Spanish (Spain)" to "Spanish (Mexico)", and if someone wants to localise the file then it's already there?