Not all lines might have been with the same line tool. You should be changing things using the Edit Selection Set command.
This will only let you later create a 2D GDL object. To create 3D GDL from a dwg, you must open the dwg as an object.
Cheers,.
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB