Some help with `%^{prop}p` usage?

For file-nodes, the %^{prompt} seems to achieve what you are going for (?) – I may not have understood the purpose of your attempt, so I may well be off the mark.

Please disregard:

  • The fact I am using lower case for property n;ames; perhaps you prefer to stick to the uppercase
  • the :modified: <> part of the template; it’s a way to insert a time stamp automatically (a tip in Org-roam wiki)
(add-to-list 'org-roam-capture-templates
             '("t" "test Org" plain "%?" :target
               (file+head "personal/${id}.org" ":properties:
:modified: <>
:series: %^{Series}
#+title: ${title}