I am assuming you can read and write normally to your external drive (sorry, I don't have a RAV file hub)
If you render the project then LF will output the timeline to produce a single file which does not store any clip information etc but will be 'your finished movie'
If you want to go back and work on a project then you need to archive it
So use Share/Export -> LumaFusion Project Package
Then select your destination
fullsizeoutput_37a2.jpeg [ 91.18 KiB | Viewed 257 times ]
If you select 'Full Original Media' you will include the whole untrimmed media (although you will only see your timeline clip)
If you select 'Trimmed Media' you will still be able to go back and work on it but you will only have a second or so either side of each clip to work on
If you've deleted everything off your iThing you can go back and restore the project and media when you're ready
Does that make sense?