It might be better to post this in the FE/Instructors forum. All the EASA regulations are available online, as I'm sure you know, so you can find the Aircrew bits here:
https://www.easa.europa.eu/en/docume...eu-no-11782011 As I'm not a TRI myself, I can't find the relevant bits quickly. Recording of flight time is now FCL.050 but I don't think it covers this situation.