Unfortunately, they’re not homogenous and elemens prior to and after the ID vary from each other.
Thanks @ScottWorld I asked the AI too to use Google’s RE2 RegEx and the regex tester shows it’s workable (/https:\/\/docs\.google\.com\/document\/d\/([-\w]+)\//) but I failed to get it work in the Airtable formula.
This appears more complicated than expected to achieve in Airtable and I’m reverting to Make.com. 