welcome to the forum,
might check out this, need to hardcode all paths including config file and location of rclone.exe
--log-file=D:/user/Documents/rclone/"log
perhaps cut and paste problem?
maybe, if you need environment variables, might try cmd /c c:\path\to\rclone.exe sync ...
or put run a command inside a .cmd and run the .cmd
something like this
for /f "tokens=2 delims==" %%I in ('wmic os get localdatetime /format:list') do set datetime=%%I
set datetime=rclone.%datetime:~0,4%%datetime:~4,2%%datetime:~6,2%.%datetime:~8,2%%datetime:~10,2%%datetime:~12,2%
c:\path\to\rclone.exe sync ... --log-file=d:\user\documents\rclone\%datetime%.log