I'm not sure what your goal is but here is my 2 cents on the matter...
Since we mostly use standard cables on our designs we model the coaxial by using a single spool with the correct coax cable thickness and connectors. This is the "STANDARD_COAX.PRT" on the attached image. It this example we might be able to use the TE Connectivity 2015357-4 (200mm) standard cable on our bom (in this case you could name the part on the design also as "te_2015357-4.prt").
In some special cases we use coaxial cable in point to point connections. Then we create a coaxial spool with the correct parameters. In this example the "CUSTOM_COAX.PRT" is a Alpha Wire 9174 BK005 spool that connects from Molex SPOX to PCB-pins. The shield connection (copper color) is not very clear and our subcontractor usually asks how the shield should be soldered/crimped...
