How to make Portfolio Link and what is Project URL (optional)?

Question

Upwork

Once I read the blog of one bourgeois and in his mailing list links to individual projects from the portfolio on the upwork site were shown. I asked the upwork support and read the documentation, no one knows how to do it.
That is, the client in the bid clicks on the link and gets to the page of the description of a particular project from your portfolio, and not to your profile as a whole.
I also can’t understand what kind of beast Project URL (optional). Is this a link to third party resources related to this project or where?
Thanks for the replies.

Answer 1

This was a test functionality that was present in some of the bids, in the end it was not implemented

Answer 2

well, as it were, yes - project url is a link to a separate site of this project or github, its sources, for example, or something like that.