@flo I know of many ways that person might have done it, but how would anyone but that person know how that person specifically did it? Why would anyone care how some particular person did got a æ character into a document? Is that actually your question? If so, please share what significance that has for you.
Your last response to me was “How do you get the a and the e to squeesh together in the following email address?” and my answer to you has three parts:
1. The æ is not part of that email address. It is a stand-in for the @ symbol, which I personally usually get by pressing Shift+2.
2. I would never think to try to put an æ symbol in an email address, and if I did try, I would fail, because that symbol is not allowed in email addresses. I might just type ae in that case.
3. If I did want to get an æ symbol for some other reason, it would depend on the context. If I were typing online, I would tend to find an example in a document (or an Extended ASCII table or a unicode character table ) and cut & paste it. Or I might use a program that serves the same purpose. If I were writing a computer program to do it, I would think about whether it was for an ASCII or unicode string, and then probably define the correct character for it numerically and use that.