Quick question…
How can I combine various gcode files into one file, so that I can arrange them to cut all the pieces out of one sheet of wood in one cut, rather than having to reset for each piece???
Arrange all your individual design into one larger design, then export gcode for all.
If you use something like UGS and have the gcode in text format, you can put them together in a simple word processor like Notepad. Then you can remove extra lines of code that may be unneeded. I do this all the time.