However, it seems that I am facing another problem: in the "Drawing preferences", only the dimensions and orientation of the page are available. The fields used to modify the margins, or the reference corner, do not appear.
Likewise, the button "Calculate the number of pages" does not appear either.
I am looking for my part, but if by chance you also had an answer to these concerns, I thank you very much.
This feature has been introduced at some point during the development of 2.2.0. So you probably have an older version. We now are at 2.2.0 RC3.
Where to get it: https://github.com/LibreCAD/LibreCAD/releases