I'd like to know if there is a specific code to mention on the API on the required field destination location code in order to have all the destinations possible from my origin location code ? or a possibility to fill nothing in the destination location code ? Thanks for your answer
I'd suggest you check out the Flight Inspiration Search API which provides a list of destinations from a given origin.
You can also have a look at this article which explains how to build an anywhere search with the API.