Me cancelaron el viaje, cosa que me fastidió mucho.
They cancelled my trip, which annoyed me a lot.
this sentence uses cosa que in the middle of the sentence
the notes state otherwise using la cosa que and it says only for beginning of the sentence not middle
am i right to conclude, cosa que = lo que in the middle of the sentence, whereas la cosa que = lo que in the beginning of the sentence.
can i also further conclude below
Le encantan los documentales de historia, cosa que/que/lo que/lo cual (yo) encuentro aburrido = I find [the fact] that she loves history documentaries boring.
cosa que/que/lo que/lo cual are all interchangeable and replacement with no change in the meaning in the middle of the sentence?
la cosa que/lo que for the beginning of the sentence.