On LibreOffice Cambridge Hackfest and the days after it I hacked on exporting custom shapes to DrawingML. (The “Part 2” in title indicates that there is a Part 1, the work I did on FOSDEM Hackfest, earlier this year.)
It was drawn to my attention, that my commits caused “regression” in the sense that the wrong export became even worse in some cases (e.g. tdf#90338). I was also aware of some imperfections.
Screenshots worth a thousand words, so here is the result of my recent work.