Learn Croatian: Osjetljive stvari sortiramo odvojeno od svega drugog. - We sort delicate things separately from everything else.

The preposition od (from) always requires the genitive case. The base word for 'everything' is sve, which becomes svega in the genitive. The word drugo (other/else) must match this case, so it changes to its genitive form drugog.

What gender is sve (everything) considered to be?

In Croatian, the concept of 'everything' (sve) is treated grammatically as a neuter singular pronoun. That is why it pairs with the neuter word drugo (else), and why they both take neuter singular genitive endings in this sentence.

Is odvojeno an adjective matching a hidden neuter noun?

No, here odvojeno acts as an adverb meaning 'separately', telling us how we sort the items. In Croatian, it is very common for an adverb to look exactly like the neuter singular form of its corresponding adjective.

I know stvar is a feminine noun. How do we know osjetljive stvari is in the accusative case here and not the nominative?

Because it is the direct object receiving the action of the verb sortiramo (we sort). For feminine nouns ending in a consonant like stvar, the nominative and accusative plural forms are identical (stvari). The adjective osjetljive also shares the exact same form for both nominative and accusative plural feminine.