The details of experiments with knotted buttonhole stitch are here-
4. In the first row, three buttonhole stitches with varying heights are worked with the knot, and two variations of this stitch combined together in the second row, and an angled version of this stitch is worked in the third row.


5. knotted button hole is worked with other stitches in these rows. The first row- pistil stitch, detached chain stitch and fly stitch are worked over a row of knotted buttonhole. The second row, the stitch is combined with closed buttonhole stitch. The third row, herringbone is combined with this stitch.


6.combination with other stitches are  continued in these rows too.
Knotted buttonhole with bonnet stitch in the first row, chain stitch with this stitch in the second row, Cretan stitch with this stitch in the third row.