Ooooh, I didn’t realize that was there. Nice.
Strange, the mouse p;ointer changes from a draggy hand (draggable) to a pointy finger (clickable) when I hover over the marker. Clicking on the marker doesn’t seem to do anything. Time to do some googling.
[edited to add I was looking at the wrong place on github]
From the code on github, [which isn’t for what I thought it was for] It appears that as well as mlon and mlat you can also include mtxt in the URL to set text for the marker [except I was looking at the wrong code]. So the standard OSMap probably doesn’t have an mtxt feature. Which doesn’t explain why the mouse pointer changes to indicate the marker is clickable.