jbissaillon wrote: The biggest problem is that I do not want to show a shape for the marker, but the selection box is grayed out.
I opened this part to take a quick look, and the Marker Polygon Shape variable is locked (twice!) in the Parameter Script, so diabling this option seems very intentional. I removed this command for the script, and now the other geometry options are available, but selecting any except the Circle option results in no marker shape (which is what you desire).
If you want to experiment, you can open this object via Open Object by Subtype... > General GDL Object > Drawing Symbol > Marker > Window-Door Marker > Door Marker_NCS 12, and do a Save As... to save a copy of the object. Now if you go the the Parameter Script and add an "!" before each line:
this will enable the Marker Polygon Shape option. Save the part and try it in your project.
This is a crude hack, I have not tested to see what other unintended consequences follow this change, but you may wish to play with it. You could also look at the bottom of the 2D Script where the variable gs_marker_shape is used.