I want to follow the advice I've read and heard to have both a main library in R_HOME/library and a user library. I'm using W10 on a desktop machine (not important, except that it gives me a name by which to refer to it), and I can't make R use the user library.
I have succeeded in doing that on a W10 laptop: C:/R/R-4.0.2/library contains some 30 recommended packages, and C:/Users/[username]/Documents/R/win-library/4.0 con contains a much larger number of packages in my user library.
As I recall, and as I wrote down when I did an upgrade on a server, all you have to do to create a site-library is to create a directory called C:/R/R-4.0.2/site-library, and R will use that the next time it starts.
To create a user library, create the directory C:/Users/[username]/Documents/R/win-library/4.0.
That seemed to work on my laptop, for I have seemingly a working R library and a user library there.
That seemed to work on the server, too: I have a library and a site-library.
In both cases, .libPaths() shows the same libraries that I see with Dired on the disk.
I tried to do the same thing on the desktop machine, and i can't make it work.
I created a directory C:/Users/[username]/Documents/R/win-library/4.0, restarted R, and ran .libPaths(); the only directory that was listed was C:/R/R-4.0.2/library.
Because I thought the Documents in that path seemed odd, I tried it again using C:/Users/[username]/R/win-library/4.0, still with no success.
https://cran.r-project.org/doc/manuals/r-release/R-admin.html#Managing-libraries seems pertinent, but I'm not sure how to interpret the output of Sys.getenv("R_LIBL_USER). I get "\\[toplevel]\[nextlevel]\Home$\[username]/R/win-library/4.0", which I presume is a long-winded way to get to /Home$/[username]/R/win-library/4.0 (aka C:/Users/[username]/R/win-library/4.0.
Suggestions? I've tried a number of other suggestions from SO, all to no avail.