You could use a list (or another associative array) as the value
Names Default To Here(1);
aa = Associative Array({"A", "B"}, {"A", {"X", "."}});
show(aa);
aa = .;
aa = Associative Array();
aa["A"] = "X";
aa["B"] = {"X", "."};
show(aa);
aa = .;
aa = [
"A" => "X",
"B" => {"X", "."}
];
show(aa);
-Jarmo