Why would a copy of the Technical Display mode change the available options. It was identical, but after tweaking a few of the settings it switched.
The main item missing is “Show Hidden Lines”
A spanking new copy of Technical works fine.
Ah, now I’ve broken that one too.
Was playing with these settings in the copies.
Done it for a third time now. I think it is something to do with changing the silhouette line width. I was changing line widths randomly and clicking OK after each of the 4 or so changes and the silhouette one seems to be the issue. Was using the value arrows on-screen.