Yes and No. You can certainly make an array whose elements consist of strings of one character long.

array[1..12] of string: my_string_array = ["1", "1", ..., "8"];

You can then join them together:

string: my_string = join("", my_string_array);  % => produces your original string.

But strings in MiniZinc are atomic, not sequences of characters. You cannot break a string into its component characters with any MiniZinc operation.

I even tried the following.

var string: left_part;

var string: right_part;

string: my_string = "114445638888";

constraint my_string == left_part ++ right_part;

solve satisfy;

Got an error message saying that ++ is valid only when its arguments are not vars.