Learn French: Prends celui qui est récupérable, c'est un jouet à emballer. - Take the one that is salvageable, it is a toy to pack.

This is the passive infinitive construction. In French, you typically use a Noun + à + Infinitive to describe an object that needs an action performed on it. Translating 'to be packed' literally as à être emballé sounds very unnatural here. Note that using pour emballer would completely change the meaning to 'in order to pack', implying the toy is a tool used for packing.

Why do we need celui qui instead of just translating 'the one' as le?

In French, you cannot place a definite article like le directly in front of a relative pronoun like qui. To express 'the one that' or 'the one who', you must use a demonstrative pronoun (celui, celle, ceux, or celles). Because we are referring to a masculine singular noun, we use celui.

Could we say il est un jouet instead of c'est un jouet?

No, you must use c'est here. A fundamental French rule is that c'est (and not il est) is required when introducing a noun that is preceded by a determiner, such as the article un. You would only use il est if it were followed by a bare adjective, for example, il est amusant.

Does the word récupérable follow a reliable pattern for creating adjectives?