Dear eIDAS community.
I like to suggest my mensch.ID project as the cross-border unique identifier that is described by “Commission Implementing Regulation (EU) 2015/1501” in Annex item 1d for natural persons:
(d) a unique identifier constructed by the sending Member State in accordance with the technical specifications for the purposes of cross-border identification and which is as persistent as possible in time.
I created that project because I’m developing a web-based Electronic Health Record (shEHRd), as a suggestion for the European Health Data Space (EHDS). In order to link health data across different countries I see a need for an ID that is easy for people to remember and communicate both in verbal, (hand-)written and electronic form and is also unique. Those identifiers already exist on a national scope in some countries, but not all. E.g. in Germany the common way of identifying a person is by their name, birth date and birth city, which is hard to reliably use for matching because of the many ways to spell a name and common spelling errors of names and locations.
My solution is hence my mensch.ID project which gives every person on the world access to up to a unique ID. Mine is 19891117-XMWT3, which I will prove to you if you challenge me through the website 
I’m looking forward to your feedback, suggestions and ideas.
Best regards,
Jan Scholtyssek