What does the pronoun "it" refer to?

Hello to anyone who bumps into this topic.

I have been reading Cognitive Grammar by Langacker for a long time. Although I find it not so difficult to read as when I start to do it, I have a lot of questions through this reading process. For example, "The subject of a clause is a nominal that elaborates the trajector of the process it designates." I have look up the word "designate" in the dictionary, but I cannot figure out the content of the pronoun "it". If "it" refers to the "nominal", what is the object of the verb "designate"? "the process" or "the trajector of the process"?

Really thankful if anyone can help me with that.