famadorian:
You are correct, the door thickness parameter does not affect the 2D Symbol. You can open the library part by selecting it and using the command
Open Object.... The Door Thickness variable is
fr_th1. You can then look at the 2D Script to see where the door thickness is drawn and change it from a hardcoded value to the variable. This may impact other aspects of the symbol, so debugging may be required. This will take some basic knowledge of GDL.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
David