Morgan@pavilion:~
$ sudo nano /etc/grub.d/40_custom
Morgan@pavilion:~
$ sudo update-grub
Generating grub configuration file ...
Found theme: /boot/grub/themes/mx_linux/theme.txt
Found linux image: /boot/vmlinuz-6.1.0-35-amd64
Found initrd image: /boot/initrd.img-6.1.0-35-amd64
error: syntax error.
error: Incorrect command.
error: syntax error.
Syntax error at line 196
Syntax errors are detected in generated GRUB config file.
Ensure that there are no errors in /etc/default/grub
and /etc/grub.d/* files or please file a bug report with
/boot/grub/grub.cfg.new file attached.
Morgan@pavilion:~
$ nl -ba /boot/grub/grub.cfg.new | sed -n '180,210p'
  180  ### END /etc/grub.d/20_memtest86+ ###
  181
  182  ### BEGIN /etc/grub.d/30_os-prober ###
  183  ### END /etc/grub.d/30_os-prober ###
  184
  185  ### BEGIN /etc/grub.d/30_uefi-firmware ###
  186  ### END /etc/grub.d/30_uefi-firmware ###
  187
  188  ### BEGIN /etc/grub.d/40_custom ###
  189  # This file provides an easy way to add custom menu entries.  Simply type the
  190  # menu entries you want to add after this comment.  Be careful not to change
  191  # the 'exec tail' line above.
  192  menuentry "Puppy Linux (BookwormPup64)"
  193          set root=(hd0,2)
  194          linux /dpupbw6410.0.11frugal/vmlinuz root=/dev/sda2 pmedia=atahd
  195          initrd /dpupbw6410.0.11frugal/initrd.gz
  196  }
  197  ### END /etc/grub.d/40_custom ###
  198
  199  ### BEGIN /etc/grub.d/41_custom ###
  200  if [ -f  ${config_directory}/custom.cfg ]; then
  201    source ${config_directory}/custom.cfg
  202  elif [ -z "${config_directory}" -a -f  $prefix/custom.cfg ]; then
  203    source $prefix/custom.cfg;
  204  fi
  205  ### END /etc/grub.d/41_custom ###
Morgan@pavilion:~