There was considerable discussion about this in the Beta group, over the year-plus-long gestation of Scrivener 3 Windows – which worked almost completely and dependably all of the time, save for ‘little’ areas of problem like this.
The actual work was very complex, and the Scrivener team were very responsive,not to say accurate, knowledgeable, and diligent.
They kept a good list, and this is on it. There are other matters probably still above it, likely including redoing of the Themes, which are themselves complicated as important portions are coded, and actually pretty important due to visibility issues on the dark ones some number our eyesights require.
I think @devinganger and @JimRac are likely close or accurate in their surmise as to lists being particularly hard, multiplied by what others suggest about QT, which has been notorious for long waits in dealing with such things. You had to be there…and yes, there are no good alternatives even yet, if a less demanding app than Scrivener could be delivered through layers of evolving frameworks.
I also note that Word itself can mess up pretty easily with lists, though it is easier to correct them there. Thus there’s a method being passed around, using a Scrivener ability to easily bring in Word to correct your iists, when you need that inside a Scrivener project.
I detailed it recently, found it works well, and you can find it here: How could one get lists to work?
I might say this is available and works due to excellent design judgement from the beginning in Scrivener…this is in a real software world.