How does one create a Data folder, if one does not program operating systems?
Your next sentence correctly answers this question.
Existing system default /Users/username/Library/Application Support/Sublime Text 3, delete or move to new? E.g., Does one create Data and add subs Data/Application Support/Sublime Text 3?
No, just the
Data folder is needed, ST will handle everything else itself. If you wanted to copy your existing settings, you can copy the contents of
/Library/Application Support/Sublime Text 3 into the
What if macOS insists on some things staying in Application Support?
Operating systems cannot require things like that or where preferences go, they provide best practice/convention and APIs to support them. It is up to application developers to handle it correctly.
Can Sublime Text be ported in this way as a var folder hidden admin app (stick or axe)?
I'm not quite sure what you're asking here, but I would assume yes.
If one did var one's editing, can copies of one's var Sublime be slapped around to different vars and regular users on the same system? (honestly liked some of my teachers back when, though ever confused)
I don't know what the term 'var' means in this question (or the previous), but what I think you're asking is if you can use this "install" of ST with different users or machines. And yes you can, it is a truly portable (granted macOS only) installation, with the only limitation (that I know of) of opened files/projects/etc will only be viewable if they are available.