In the xml view of model A, add the following attribute to the x field:

options='{"create_name_field": "y"}'

I found the solution while debugging in javascript in web/static/src/js/view_form.js and found the following function:

add_id: function(id) {},
_create_context: function(name) {
    var tmp = {};
    var field = (this.options || {}).create_name_field;
    if (field === undefined)
        field = "name";
    if (field !== false && name && (this.options || {}).quick_create !== false)
        tmp["default_" + field] = name;
    return tmp;
},

this.options corresponds to the options attribute in the field of and xml view and create_name_field corresponds to a dictionary key.