Thank you William - that preset works well!
Hi Seguis,
It is nice to hear your feedback.
Not log after you asked this question Madhu posted a much better solution.
https://moodle.org/mod/forum/discuss.php?d=345289#p1392541
I made a simplified version for you.
As in Madhu's preset, use dropdown menu will be easier to specify a set of choices.
Thanks to Madhu.