Great work! I'm wondering if you could leverage DiscMaster or my Macintosh Magazine Media collection to hunt for themes? You'd just search for the type or creator code. Not that you're short of themes. I did this sort of search recently for tilesets for MaciGame and found over 350 plus I am notified of any new additions thanks to DiscMaster search RSS https://news.ycombinator.com/item?id=43551222

Here you go – I took a look on a Mac OS 9 VM, and the System suitcase is what you want; MENU resources; resource ID -16489 on here but expect that to vary by version. Select the menu item you want and you can set a “CMD Key” in the bottom right corner https://i.imgur.com/wcqQ27j.png

Don't do this on the running System suitcase. ResEdit will warn you about this too. Make a backup copy, make your changes to the backup copy, then boot from some other blessed System Folder (install CD is fine) and swap them out.

The mindset where you can edit anything on everything is what we truly lost when we lost the Classic Mac OS. These themes are merely one embodiment of that mindset. It's just Resources all the way down; Any user-facing String, any UI graphics, any icons, any cursors, any sounds, any menus, any window definitions, any dialogs. ResEdit can even be extended to support editing custom (non-Apple) Resource types, to say nothing of the more powerful third-party Resource editors like Resourcerer.

Applications' code even lived in `CODE` resources in the original 68k days before the era of PowerPC and Code Fragment Manager moved that stuff to the Data Fork. A classic 68k-only Application would be a 0-byte file if one copied it to a PC improperly and discarded the Resource Fork. It's literally all Resources and that's so cool!

Here's Apple's ResEdit Reference if you need it: https://developer.apple.com/library/archive/documentation/ma...

Relevant Folklore: https://www.folklore.org/The_Grand_Unified_Model.html

Relevant Inside Macintosh: https://vintageapple.org/inside_o/pdf/Inside_Macintosh_Volum... (warning: massive PDF)

I highly highly recommend you and anybody else interested in Classic Mac OS spend some time with David Pogue's excellent Macworld Mac Secrets 5th Edition: https://archive.org/details/mac_Macworld_Mac_Secrets_5th_Edi... (there's a 6th edition that covers early Mac OS X topics, but that just muddies the water)

edit: and keep your unmodified System suitcase backup somewhere besides the System Folder to ensure the Startup Disk control panel can't “bless” the unmodified one instead of the edited one. You can tell which suitcase is “blessed” because it will have the “Picasso” Mac OS face laid on top of the regular suitcase icon: https://en.wikipedia.org/wiki/System_folder#Location_and_%22...

Thank you for the very detailed response! Appreciate it!