I meant to make this a DRAFT PR, but I don't seem to have the ability to get to that UI now :-/ . Should not be merged without additional work (e.g. see TODO markers).

While one might release a complete system as a sysout, that's not the way that most people would share reusable smaller pieces of code (e.g., look at the things in "lispusers"). You expect your running Medley image to be long-lived - you can logout and restart from where you left off - continue your development, debug your functions, and so on - but at some point you're highly likely to want to save your sources in an organized way, throw away system state that is no longer useful, and start over from a clean system image (e.g., back to a full.sysout). You save your sources using the file package, where you create (a list of) file commands that direct the file package what things to save on the (source) file, initial values of variables, and so on. There are, of course, tools (functions) that help you do this. See section 17 of the IRM. This is how the source files for Interlisp are managed, and the library packages, and the lispusers packages. You don't ever edit the (not quite plain) text file using a text editor - you edit the structure of your code in the running system and then have the file package save anything that changed, you might compile that file, you might also have the system run the compiled code rather than the interpreted code in your running image - and so on around the exploratory development loop as you've described.

i sent @sgharms an invite to the Interlisp organization and the website group.
@abhikhasnain1 has been working on a rewrite of the Medley primer.

@sgharms Thanks for sharing your perspective on approaching Medley.

@nbriggs Fabulous. I don't know how I missed the IRM in earlier clonings of repos, but I'm definitely integrating it into my thought process now. Thanks for the anthropological context you provided.

@abhikhasnain1 Let me know if I can be helpful to other initiatives you have underway.

Re: "Use a metaphor of branches, and then a "merge" to the base SYSOUT a la git-based workflow"
That really isn't the mental model that I'd expect people to work with. Saving a sysout is more like SBCL's "save-lisp-and-die" functions: except it doesn't die, and since it's an image of a virtual machine memory state it's not limited to being restarted on the same hardware that you created the image on. Calling '(LOGOUT)` is conceptually close to "save-lisp-and-die" -- it saves the virtual machine state in a file typically named "lisp.virtualmem" (which is identical in format to the result of calling SYSOUT or MAKESYS, modulo the amount of cleanup done before exit/after resume)