If, however, I use org-roam-insert to link to the file with the headings, all links with org-ids also show up in the backlinks. It appears that somehow the database is not updated. Is there anything I can do to fix this behaviour? For reasons of long-term preservability I am strongly preferring the use of org-ids. Thank a lot.
Thanks for the reply. If the backlinks with org-id show up, they work fine for me as well. My issue is that the database is somehow not updated when I use org-store-link and org-id is active. For what it is worth, I even did a org-roam-db-clear & org-roam-db-built-cache and they would still not show up in the backlinks. Only if I use org-roam-insert to the file which contains the headline, the database is finally updated and they show up. They remain there even if I remove the link afterwards - so that is a workaround, but still not a good solution.
Offtopic: how do you create the #+created: & #+last_modified ?