Sets specific config fields for a variable. Only non-default values are persisted to the options file.
config.set(var_name, ..., options_file_name = NULL, options_dir = NULL)[list] The updated fully-resolved data config (invisibly).
[character] The variable name to configure.
Named arguments for config fields to set
(e.g., bma = TRUE, bma_to_log = TRUE).
[character, optional] The name of the options
file. If NULL (default), the user will be prompted interactively.
[character, optional] The directory containing options
files. If NULL (default), the default directory is used.