@chriddyp I came across this post as I was describing for another user how to do this - just to standardize terminology, I think you mean:
[min, q1, q1, median, q3, q3, max]
There are an infinite variety of ways to do this, but the one I’ve used is:
[min, q1, median, median, q3, max]
This is actually used internally by plotly.js to construct candlestick charts out of boxes, using q1=open and q3=median=close - mine has one less duplicated value, though it occurs to me that your version is probably robust in other box plot software that makes a different choice of how to calculate quartiles - as discussed in Boxplot quartile seem’s wrong