***Update***********************
I also have this problem in the latest windows installation—on the same machine that long filenames were never a problem before in Maxima. To fix it choose the sbcl version of maxima, as described at My Windows Installation.
*********************************
I have a student running wxMaxima on his windows laptop. He has partitioned his hard drive so he can run Windows 10 as well as other operating systems.
When he attempts any plotting command, he gets an error:
The part of the error message with directory name TANUSH~1 says to me that there is some problem with the long directory name, possibly also a problem caused by a space in that directory name, possibly due to the way those new partitions are formatted.
As a workaround, we set the maxima option maxima_tempdir to point to another directory and all worked as expected:
Of course, that new directory will now fill up with files with names like maxout_xxxx.dat and maxout_xxxx.gnuplot, but that was already happening in the default directory. A natural feature for wxMaxima to include in future releases would be to clean up the directory by deleting all those files when the program is stopped…
The MaximaList 
You can create your maxima-init.mac file with all the commands you normally use and don’t want to type each time. In this file you can also define the path to maxima_tempdir so all the files maxout_xxxx.dat and maxout_xxxx.gnuplot will be dumped here. For example, I have:
maxima-init.mac:
linux → /home/your-user-name/.maxima/maxima-init.mac
w7 → C:\Users\your-user-name\maxima\maxima-init.mac
maxima_tempdir:
linux → /home/your-user-name/Documents/maxima/tempdir/
w7 → C:\users\your-user-name\maxima\tempdir
Hope this helps
LikeLiked by 1 person
Thank you for this helpful information which occured with my new office computer.
With W10 I had some troubles to save the .mac files after writing because wxmaxima always did save it as .wxmx files.
After resolving by using only the Windows-Editor it is working fine!
LikeLike
Really helped me out!
LikeLike