For example, you can make customization by using the form elements in the following file. Sample file > Please Click.
All the form data you have edited in theme-settings.php run the change_settings() function in the theme.php file after clicking on the "Update" button on theme management.
The data from the form is processed in the change_settings() function and then returned as "Array".
Then, it is saved in the [settings] array in the theme-config.php file located in the theme directory.