Thank you for taking time for your patient answers. So according to that help article, Dorico should have created the bar before the bar I selected the last note from. (It doesn’t say that you should select the first note of the bar, does it?) Instead, it creates one bar after the note I select (which is inconsequent with the help file but feels very logical to me), and as a bonus it removes music.
Thank you again for your answers, but as I said I have already worked around it and this is merely a bug report which I hope is useful to the developers.