I agree that the presentation could probably be improved, though I'm not sure yet how.

The new linetype names and descriptions are defined in the .lin files read on start up (qcad/lintypes). This improves compatibility with other CAD systems and allows users to define their own custom linetypes. QCAD needs to present these names / descriptions to the user somehow. In QCAD <= 3.6, this was not a problem since there were only a few, fixed linetypes. In QCAD 3.7, anything can be defined in those .lin files. So name and description is all there is to show really.

For existing drawings, the linetypes are read from the DXF/DWG file. Also in this case, the name and description is defined in the DXF/DWG file, not by QCAD anymore.

Any thoughts?

Changed from bug to task as this is definitely not a bug, but could probably be improved with a good idea which I didn't have so far ;)

I will think about it ;-)

Ok - I see - it's a tricky file ....
If I change a Line Name in the .lin I will still have the original Line Name in the Layer Linetype List - regardless that this name is not anymore used in the .lin file?
What means: The same linetype - twice in the layer list - with different names but only once in the .lin file. I do something wrong ....

Ok - is there some kind of "Edit instruction" available for this .lin file?

Editing the types defined in the .lin files is generally not a good idea, as these names, descriptions and type definitions are defacto standards across CAD applications.
The files are mainly useful to add your own types. Preferably, you would add your own types in separate .lin files in the same directory, to make updating easier.

There's plenty of information available about .lin files. Just google for "autocad lin file format" or "autocad custom line types".

Note that these line types are always loaded for each new or loaded drawing. If a drawing is loaded, the line types from the drawing are added to the list and existing line types read from .lin are overwritten. This is the effect you have likely experienced when editing the .lin files.

Ok - I'm now on a learning curve ........ ;-)

Question: I'm trying since hours to make following Linetype working - but I can't figure out what I'm doing wrong:

*HOT_WATER_SUPPLY,Hot water supply ---- HW ---- HW ---- HW ----
A,0.5,-0.2,["HW",STANDARD,S=0.1,R=0.0,X=-0.1,Y=-.05],-0.2

What is the trick?

Only simple line types (i.e. dashes) are supported at this point.

OK, I've come up with an alternative presentation of the line types combo with a decent preview.

Looks much better - can't wait to see it by myself in the next update. ;-)