The command dpkg-repack can help you by following way:

1. First List packages required for installing Desktop-Environment (Here example for xubuntu-desktop:

   
   
   

   sudo apt-get install  xubuntu-desktop -s | grep Inst | cut -d " " -f 2 > file1
   
   

   
   
   

   Above command writes required packages' list for xubuntu-desktop in file1.




2. Use Try without installing option from live Environment from ISO (By either of 2 ways):-

   
   
   
   
   
   • Add entry of ISO in GRUB and directly use Live Environment (try OS without installing)
   
   
   • Burn ISO to DVD and go for Try Without Installing
   
   



3. On Live Environment Run following command:

   
   
   

   sudo xargs dpkg-repack < file1
   
   

   
   
   

   Above command dpkg-repack creates deb files (in the directory where command is run) of all packages listed in file1 because Xubuntu's Live session contains all packages in installed condition! (Move/Copy them to your storage)




4. Now You've all required debs in a directory. Restart and come Back to your Ubuntu (Default) OS and install packages either of following ways:

   
   
   
   
   
   • cd to directory containing all debs and run dpkg -i *.deb
   
   
   • OR (Recommended as standard method is APT) Install with help of Local repository
   
   

In brief : By this method you can get required debs by dpkg-repack from live session of distro's ISO and install them to current OS

Note/warning: Here same version of Ubuntu & Xubuntu used if there is old/update then dependency issues may brakes/downgrades current packages