Excel Lambda function to convert an array to a list

flatten.txt

FLATTEN = LAMBDA(array,
    LET(
        //name definitions
        rows_, ROWS(array),
        cols_, COLUMNS(array),

        // index the zero-based array
        seq_, SEQUENCE(rows_*cols_, 1, 0, 1),

        // row and column indices
        row_, INT(seq_/cols_),
        col_, MOD(seq_, cols_),

        // return
        // get array cell by row and column index
        INDEX(array, row_ + 1, col_ + 1)));