I’ve played a bit with both options, and it would seem that spiting the table of categories in half rather than sequentially is better for our purpose.
However, it is tricky to control where it should split.
I was able to achieve this in my browser:
But only when I artificially placed the categories on the left in a div (to prevent it from splitting too early, otherwise the Measure root category goes to the right column):
Is there a way to ‘pack’ the rows with specific category IDs into the DIV, maybe via the theme api?