I got into my head to make a specific cable pattern for a pair of longsleeved, fingerless mitts I'm planning to knit. I made a drawing, and sketched it out on grid paper. I wanted the cables to be single stitch, but wasn't sure how to get it out on my needles.
I took out Alice Starmore's Aran Knitting, that I bought but haven't knitted anything from yet. In it, she has some useful pattern swatches, that was a great help. In particular, there was a stitch that ran "slip 2 st to cn, k1, sl p st back to left needle, purl, k1 from cn" that was exactly the stitch I need for my crossing cables. I knit a swatch and it turned out just as wanted it. Then to chart it I had to go on knitting so I could write down the stitches in the chart as I was knitting them.
Different pattern authors seem to use their own individual symbols for cable stitching patterns so I feel no shame in having invented a few symbols of my own. Some of them look like little elephants on the page.
I am particularly pleased that something that was only in my head a few days ago turned out so beautiful when swatched. The yarn is Studio Donegals Donegal Aran Tweed, in lavender. Colour of the yarn is seen better here.