Yes - ideally there should be a standard library for this. There is no reason the GUI cant update the config file and refresh from it when it updates.

A convention for writing JSON, YAML, or whatever config files that standardized types of options, their default, and something about their types (is it a toggleable boolean, a bounded continuous value, an integer, etc etc) could be nice. It might be possible to provide enough info automatically generate the GUI (draw the first as a button, the second as a slider, and the third as a number box), and that sort of info would be helpful to have if you were writing the file by hand anyway.