Thank you for your replies.

I wrote more after the quotes below.

Ihor Radchenko <yantar92@posteo.net> writes:
> I wrote https://github.com/yantar92/org-capture-ref to do exactly
> this. 

Is it meant to be used with org-ref ?

I didn't plan to build a bibliography with bibtex (at least for now). I
just plan to built a simple book reading tracker with Org-mode. But I
keep a note about your suggestion, it could be very helpful in the
future.

Thank you very much.

Ihor Radchenko <yantar92@posteo.net> writes:
> Yes, but passing non-standard data is an undocumented feature. (It is
> stored in :query property that you may need to extract via
> %(plist-get (org-capture-get :query) :my-keyword) placeholder or
> something similar.

Thank you for the info. I will take a note about it.