You can do that in a simple text editor and save the positions you want. You can do it a number of ways but it would probably be best to do it in PGN format with the appropriate headers, though I don't know what most apps require as minimum.
You could also just store the positions in a chess database program, I use SCID vs PC. Then, if you ever needed the full PGN, you could export that.
I would like to make a file with multiple positions for chess lessons in my club. Can I do that on chess.com or do I need to use Notepad or some other program.
I was hoping I would be able to cut and paste a position and then add another position perhaps by separating them with a semicolon or some such.
I would like to be able to create a file with multiple games in PGN format also.
I would appreciate any help I could get.