Hi Art.
For Windows 10, the %AppData% path should be used. (Type in %AppData% in the windows search box, lower left corner of Windows 10 screen.)

I would suggest first that your C:\Users\<yourUsername>)\AppData\Roaming\Moi folders be unhidden.
(Google "unhide appdata folder windows 10") ...show hidden folders.
Also helpful is to set up a Library "MoiAppData" in File Explorer, for this path to ...AppData\Roaming\Moi, for quick access.
My Library link usually does not show the \Moi text, but the subdirectory is there.

The contents of this ...AppData\Roaming\Moi directory may be:
Folders:
commands (my extra non stock moi _scripts)
customui
nodeeditor
objects
snapshots
startup

There may also be some misc. files there, like MoiColors, moi license keys, etc.

- Brian

I scanned this topic back 2 years, and did not see comprehensive instructions for install in Moi v4 beta,
although a lot of issues were addressed.
I'd say follow Max's original instructions, but use %appdata%.

Mac link: https://moi3d.com/forum/index.php?webtag=MOI&msg=6507.404