Racks let you organize the plugins in a song into self contained units. eg: combine your favourite instrument and effect and group it into a single unit.
Blockquote Solo and Lite don’t support linked racks but you can re-use racks across songs by copying them:
Use copy/paste — right-click on the rack in the song and select “Copy” and then paste in the other song.
Exporting racks — open the rack and choose File → Save Rack Copy As… to export the rack to a separate file. Then insert in the target file by choosing Add Object → Embedded Rack (From File).
I’m on Solo, but I cannot see the second option. There is no “Save Rack Copy As” in the menu, just “Save Song Copy As”.
The “Save Copy As” command changes according to where focus is. If you’re in a song it’ll say “Save Song Copy As”. If you’re in a rack it’ll say “Save Rack Copy As”…
ie: The “Save Rack Copy As” command only appears when focus is in a rack.