"Ultima VII The Complete Edition.boxer" is the boxer wrapper for your DOS program. If you have Boxer installed on your system, you can run the program inside the wrapper by simply double clicking it. You should even be able to open such a packet and run contained DOS programs by double-clicking them.

If that works, we can write a little batch file to start the cheat mode:
- Open a new plain text file.
- Write only one line:
serpent manimal
- Save the file as cheatmode.bat
- Drop cheatmode.bat into the same folder where serpent.com is
- Once inside double-click it.

Wow... so I actually just managed to run cheat mode from launching the game in Boxer. Great! But running the game from inside boxer leaves me no access to the saved games I had when launching from the GOG-installed link. Sigh. Pretty much back where I started, wondering how on earth I can get to the DOS prompt from the GOG launcher.

By the way, thanks for all your help thus far DeMignon. Wish I could be more cooperative ;)
Ok. Tried that. Not working from the GOG launcher.

You're welcome! I only wished I'd have a Mac here ;-)

The save games are usually stored in the same folder as serpent.com.

They are named:
GAME00.U7
GAME01.U7
etc.

If you find them on your system and copy them into the mentioned folder, you should be good to go.
After you don't need the cheat anymore, you can still copy them back to their old/original location and use the standard GOG installation again.

I don't see anything with the .U7 extension or anything that looks like a saved game file in that folder, or nearby folders... If I could just find the saved game files I think this would all work out. Any other suggestions as to where to find them?

Look in Library/Application Support/Boxer/Gamebox States/

There might be a folder for every DOS game. As I just found out, the saves are stored there, because OS X apps should not modify themselves and therefore shouldn't write in their own folders (if you try, you'll have to run the app with asministrator rights). Hence the GOG boxer version creates a shadow folder, which is used by whenever a game tries to write something (and also reads first from this location). Probably your saves are there.

Too good to be true. My "Application Support" folder doesn't have a "Boxer" folder. Odd, seeing as Boxer is most definitely installed and functioning on my computer.

I did find the folder (called "Dos Games," located in the directory with my username) where my Boxer games are installed and collected, but I'm still unable to locate any saved game files in there.

Well let's go brute force and search for them. Press Command-F to open the Find dialog and search for the extension U7

Wait wait I just found the "Gamebox States" folder you were talking about! It was in a different "Library" directory. Okay, but so, inside there still isn't anything with the .U7 extension. The only thing in the folder for Ultima 7 is a file called "Current.boxerstate". Is this what I want? Can I move this file, and if so where to?

Try looking inside.

Haha... yes! You were spot on. I tried launching the game from Boxer and my saved files are working! Very pleased....

And now I can't remember how on earth I got the cheat mode working. It was like an hour ago and it was some very arcane thing I typed into the prompt... I don't think it was any of the things you mentioned. One website I looked at said type in "serpent manimal spam s" into the prompt. My prompt doesn't accept "serpent" as a file name, only "ss" but now it seems no matter what I type in with "ss" at the beginning, it just runs the game proper but without activating any cheat mode. So close...

Update: SUCCESS!!!!! We have triumphed!

I had to go into ssconf.bat in the prompt, then exit out of it, to get to a prompt showing "C:/U7/SERPENT/ ...into which I typed "serpent manimal" with the .conf file inside the game package edited the same way. It wouldn't accept "serpent manimal" until I went into and out of the ssconf.bat file first.

What a wild, incredibly nerdy ride. Thanks for all your patience and wisdom, DeMignon. I owe ya one!

Don't mention it, I'm happy it works! My input would have ended after one post anyway, if you had used a PC ;-)