what does "from before" mean here?

I have encountered from before throughout my life although I cannot find literary examples. For example: "I knew him from before the war" = "I knew him during some period that preceded the war".

This is how the phrase is used here. "A story of detention is a catalogue of things destroyed: not just years lost to captivity, but all of life's labour from before" = "A story of detention is a catalogue of things destroyed: not just years lost to captivity, but all of life's labour during the period that preceded captivity". In this case the terminal ... captivity is implied by its previous mention, rather than explicit as in my ... war example.

I don't think this is standard usage, considering "from" is a preposition there and should be followed by a noun and and not an adverb. (I'm not fully clear on this point, though!)

As for the meaning of this part of the sentence, it is that whatever hardwork or toil one has done before one's detention, it all goes down the drain.