In that sentence, "which" is the direct object of "make", so no, you cannot add "it" after "make" because then it would have two direct objects, which English grammar does not allow.
The deeper structure looks like this:
We're in the reception area. We try to make [the reception area] attractive and welcoming to visitors.
The phrase in brackets [] is the direct object of "make". To turn the second sentence into a relative clause, we first replace the repeated phrase "the reception are" with "which":
We're in the reception area. We try to make [which] attractive and welcoming to visitors.
"Which" is now the direct object of "make", and represents "the reception area". The last step is fronting "which", leaving a blank behind, which isn't pronounced nor marked in any way:
We're in the reception area, which we try to make _________ attractive and welcoming to visitors.
English speakers understand that "which" is the object of "make" because in that clause it has to be either the subject or an object, and there's already a subject, but "make" is missing its object.