contentDeepToString

Returns a string representation of the contents of this array as if it is a List. Nested arrays are treated as lists too.

expect fun <T> Array<out T>.contentDeepToString(): String(source)
fun main() {
    val nestedArray = arrayOf(
        arrayOf(1, 2),
        arrayOf(3, 4, arrayOf(5, 6))
    )

    println(nestedArray.contentDeepToString())
}

Source