I would like to add some custom config variable in the wp-config file (not in the functions.php). Then, I need to access to these variable in my templates. What is the way to do it ?
Why do you need this?
In wp-config you can set defines. They will be accesible everywhere without needing to use globals. Define something:
Then in your templates you can show the value like this:
Or set the value to a variable: