Say, I go to http://maps.google.com (which these days redirects to https://www.google.com/maps) in my web browser. I can use the Search, and when my address is found, a (red) marker is added on the map. I can then copy this link and send it to someone else - and this works "anonymously" (that is, I don't have to be logged in to Google to do this). When the link is then opened, the marker is there.
How would I go about adding a second marker on the map like this? If I do another search, and a location is found, then the previous marker is deleted, and a new marker added at the new location - the link then changes to point to the newly added location, without reference to the old one.
I guess one way to do it would be to make a "custom map", as per the answer in How to highlight an entire route or way on an online map? - but requires that you are logged in with your Google account.
So how could I add multiple markers anonymously, and generate a shareable link to a map containing all of them?