custom-add-frequent-valuecustom-add-frequent-value is an alias for `custom-add-option' in `
custom.el'. (custom-add-frequent-value SYMBOL OPTION) To the variable SYMBOL add OPTION. If SYMBOL's custom type is a hook, OPTION should be a hook member. If SYMBOL's custom type is an alist, OPTION specifies a symbol to offer to the user as a possible key in the alist. For other custom types, this has no effect.