You're very welcome.
I actually only started playing with Calibre again. I've been revamping my entire library 2-3 times a week as I try to figure how best to arrange it (for easy browsing with Dropbox) while still providing good organization with my current ebook reader app (no support for custom columns so everything has to be in tags). The sublist thing, I just played around with last weekend.
Calibre templates are quite robust and there's a very good tutorial/manual here:
https://manual.calibre-ebook.com/template_lang.html
and a list of available functions:
https://manual.calibre-ebook.com/gen...plate_ref.html
If you click on the Template Editor button while on Save to Disk, you can even see a preview of the template's output, see the various available functions and test them out.