WoW:API SetCVar

SetCVar("cvar",value{,"scriptCVar"})

SetCVar allows you to set the content of the variables defined in the config.wtf file (which is in the WTF directory).

Settings changed in this manner are applied to the game UI immediately, however settings are not saved until exit and settings which were previously not defined in config.wtf are not available to GetCVar until the file has been saved (at logout).