Creating Custom Hook for my plugin

First, register the filter hooks with the handy apply_filters tool:

function wpse_238394_org_types() {
    return apply_filters(
        "my_org_types",
        array( "affiliate", "direct", "bureau" )
    );
}

Now, wpse_238394_org_types() will return the default 3 types being not filtered yet, so we one more custom type:

add_filter("my_org_types", function($types) { 
    $types[] = "custom_type";
    return $types;
});

Now if you debug wpse_238394_org_types() it should be including the custom_type item along the defaults.

Hope that helps. Please also take a look at the docs https://developer.wordpress.org/plugins/hooks/creating-custom-hooks/ as jdm2112 suggested.