Inserts a value into the string list at the specified index. If a delimiter is not specified then the default value of ',' is used. The index for lists starts at 0
listInsert(list, index, value)
listInsert(list, index, value, delim)
[r: listInsert("This, a , test", 1, "is")]Returns This, is, a, Test
[r: listInsert("This: a: test", 1, "is", ":")]Returns This: is: a: test