I'm having this problem in Archicad 18, i downloaded a chair from BimObjects and it has the extention .gsm, when i tried to open it in Archicad it appared this : "the selected file is not a General GDL file. Please select a valid GDL file. "
How can I open .gsm files?
If I'm not mistaken, you can load a .gsm via the Objects Toolbox.
Open up Objects and there should be a small icon with a plus sign on the bottom left where you can load .gsm files
