Would anyone have any insight to offer into this section of Varro’s Menippean Satires? It’s from the section “Eumenides.” I’ve been trying to parse it but I can’t get much further than
“Before I would respond, I do not know who indicates that the thing occupies the door”?
Which doesn’t really seem to make much sense. My instinct would be to pair nescio with the infinitive indicare, but is this misguided?
Much appreciation to anyone who can help! 
I can’t say I understand this myself, but I can offer one point: nescio quis is an idiom, with both words taken as a single unit, meaning “someone or other”. It doesn’t introduce an indirect question – it’s not “I don’t know who”, which would require subjunctive occupet instead of indicative occupat.
foris could be either accusative plural “doors” or adverb “outdoors”.
occupare + infinitive can mean “to do something first” or “anticipate in doing something”.
Some context would be helpful. This doesn’t seem to be complete.
…I thought that Hylander’s post explained everything about it, even if he doesn’t think so.
responderem is the anticipated action
foris nescio quis is the subject of occupare and the infinitive phrase
res indicare is the action that happened instead, res being an object of indicare, not a subject
Not the most illuminating of Menippean fragments. This one’s evidently prose, not verse, and the meaning seems to be something like “Before I could reply, first someone outside reveals the situation.”
occupo works like Greek φθάνω, but with infinitive not participle.