This is how you would say this in English. It would be very strange to say "These are Morag and Anna", if that's what you're thinking.
I can't explain my native language very well technically, but I think I would only use "these" with plural nouns, e.g. "This is Morag and Anna. These are their parents".
But it's plural! Therefore, "Anna and Morag are ..." and it doesn't matter if the verb is in front or after the noun. Even if nobody uses "these are" doesn't mean it's incorrect, does it? There are many phrases people use regularly in spoken language that are grammatically incorrcet (every language), people use them anyway :(
""Even if nobody uses "these are" doesn't mean it's incorrect, does it?"
That's exactly what it means. Languages are not systems of formal logic, they're systems of conventional practice. What is "correct" is defined by what people who speak the language actually do. If something is common usage, that's what makes it grammatical.
I agree in so far, that languages are always developing further and diversly. But for a fixed point in time, there have to be at least some rules to adhere to, otherwise learning a language would be rather pointless and actually having a conversation would be quite challenging. That's also why we have dictionaries and grammar books ... to look these current rules up. Additionally, I always thought, the differentiation between singular and plural to be one of the most static grammer rules because "one object/person = singular and more than one object/person = plural" is easy to remember and implement. Apparently I was wrong.
Nevertheless, there appear to be two solutions to this phrase (see comments by others). If we discuss any longer we might be able to find even more. Why don't we just agree on a difference of opinion and add to the solution possibilities?
Just because I live to be defiant, because I believe it to be more grammatically correct at this specific point in time, also because I appreciate my friends, family and colleagues as individuals, and they do not deserve to be treated as a singular person, I will keep introducing them with the words "These are Morag, Iain and Anna." or even indivdually "This is Morag, this is Iain and this is Anna.".
'This is Morag, this is Iain, and this is Anna' is the best way of introducing more than one person by name. This can be shortened to 'This is Morag, Iain, and Anna'.
'These are Morag, Iain, and Anna' doesn't work because while you are talking about more than one person, they are collectively one group.
You could say, 'These are my friends Morag, Iain, and Anna', but only because the word these is referring to my friends.
A brief explanation here: https://learnenglish.britishcouncil.org/english-grammar-reference/demonstratives
It's a bit off-topic, but may I ask why you decided to learn German at school and university? Didn't expect German to be a common language course in Scotland. I'm a bit surprised it is offered at all...
And thanks, I feel flattered. Unfortunately there aren't many chances to practice English here, we live in a slightly rural part of Germany. But if everything works out, we'll visit the Outer Hebrides again in 2021! :)