I remember reading on here that you can simply move some folders like a User Folder or two to the second drive as long as you left behind ?- something to indicate where it is to be found! I can't remember how to OR WHAT to leave as a re-director of the moved Folders so your OS can find it, but I remember very well it was on this site and back in the days Windows 7 was the way to go! I also remember after someone made the directions, someone else commented that the FREE (at that time) a program called D-linker or Dlinker, that would leave behind the marker to redirect the OS to the other drive for you.
I downloaded the D-Link Program and I am in the process of combining two 250 Intel SSDs of the 335 Series so I will began my search for it tomorrow as I saved it to CD!
I wish I could remember more about how to do it manually, but I am not that computer savvy! I can't image what you would leave in place of a moved Folder so the OS would go to the other SSD to access it! They were away smarter than I!