Go to steamapps>common>Portal 2>portal2>puzzles, then go to the folder that was most recently modified (if the map you're looking for is recent).


In this image, I would go to the folder at the bottom.



From there, find the .p2c file that has the same Date Modifed in File Explorer as Last Modified ingame.

eg.

< Ingame

< In File Explorer



If they match up, this is your map!

(To double check, look at the .jpg with the same name in File Explorer and see if it is the map you're looking for)

This part is pretty straightforward.

What you're going to want to do is simply copy and paste the map into the same folder.

Then, get rid of the '- Copy' at the end of the file name and rename the file to something else. What I do is just add 1 to the number. (eg. 1664589423.p2c -> 1664589424.p2c)

When going into the Portal 2 Puzzlemaker, a duplicate of the map should be there!

If you have any questions, put them in the comments and hopefully someone will help you out, but I won't because I can't really be bothered (lol)

Have fun!