Can you explain the grammar in this sentence-- they know that too much complexity leaves open many avenues down which the negotiation might meander to its demise?

Answer 1

The explanation is that this sentence attempts to appear scholarly or scientific by avoiding simple declaration in favor of convolution, wordiness and mixed metaphor. If you meant " How the heck does this clunker work, anyway?" it goes like this:

The subject is "they." The verb is "know." The direct object of the verb is the independent clause "too much complexity etc etc." That clause has a subject: "complexity" whose verb is "leaves" of which the direct object is "avenues" modified by the dependent clause "down which etc etc." That clause also has a subject "negotiation" and a verb "might meander" and the prepositional phrase "to its demise."

In good English, the sentence would read something like: They know that keeping it simple will help the negotiation continue.

Answer 2

This sentence uses a noun clause ("that too much complexity leaves open many avenues") as the subject of the verb "know." The phrase "down which the negotiation might meander to its demise" acts as an adverbial prepositional phrase modifying the verb "leaves open." Overall, the sentence conveys the idea that knowing the negative effects of complexity in negotiation prevents potential outcomes that could lead to failure.