I have found that global truss [1] has a download area for truss definitions as DWG-files. these files can be converted to DXF using the Teigha File Converter [2] and after that imported to Blender [3]. After that import you can create elements for the 3D view in QLC+. Seems to work. Maybe other manufacturers offer also these DWG files.
[1] https://globaltruss.de/Downloads/
[2] https://www.opendesign.com/guestfiles/t ... _converter
[3] http://blender.org