Op do 28 feb. 2019 om 08:51 schreef Cecil Westerhof <cldwesterhof@gmail.com>:

I can set a checkbox to intermediate with:
C-u C-u C-c C-x C-b

But I want to do it with code. How would I do that?

Found it. Quit simple:

    (org-toggle-checkbox '(16))

Cecil Westerhof