Shi

Let me break it down:

In Thor 1, Loki managed to change Thor's personality in a completely unexpected and unplanned way, with him stopping the coronation, made Thor got banishment so he has character development (although I think it was a bit too forced in the movie). Loki manage to save Thor from the arrogance, from his ego, from himself, even if it's not planned.

I just cannot denied through Loki action we got this Hero Thor.

But what about Loki? Thor can't save him from the truth, he can't save him from betrayal, he can't save him from mocking, he can't save him from himself, and he can't save him from falling.

In Avenger we can see a major change of Loki personality and his anger, his madness, maybe even mind controlled. Thor manage to beat him, but not save him. I just still can't believe the one who say miss you is Loki, I think he mean it that time, if just Thor had approached him with gentleness rather than anger, he wouldn't have had to destroy the plane really, he could have approached the humans and talked instead of kidnapping Loki, perhaps the story would have been different.

Imagine Thor with teary eyes, crack voice, saying "Brother, I miss you." Instead of "Listen well brother...," with his angry voice, maybe Loki action will be different.

In the Thor the Dark World, we see how Thor offer him a death and a death deal for his help, after ignore him and let him in his cell not let him seeing his mother funeral (it was Odin sentence Ik, but still it's so cruel, since when Odin sentence stop Thor? He ignore his father sentence for everone else, his mother, Jane, his ego, but not for his little brother, at least he can broke the terrible news to his little brother by himself not by some guard) the one he truly love, not even a single kind word he gave it to Loki, Thor just can't believe Loki has good in him, he can't believe Loki can change. Thor only knew him as the God of Mischief not as little brother who need help and guidance.

And then Loki getting killed, or Thor think so. Again Thor can't save him.

Then Ragnarok came well I dont really have much think to say in this movie, this movie is like "Finally Thor gave Loki the right things to say" kind of vibe. Thor told him he can do better than being the God of Mischief, he said not with an angry voice but with gentleness that he thought the world of him, he trust him with the Surtur and destroy Asgard.

Ofc there a 'but' in this, Thor CAN NOT save him in the 10 MINUTES of Invinity War, Loki manage to save Thor by giving the tesseract, he gave him a meaning full speech "The sun will shine on us again." But there no us, only Thor. Again he can't save Loki.

What if Loki:

After Avenger 1, and he became short of Avenger (What happened before that I leave it to your imagination) Tony introducing him to films, they have time to watch movies with the whole team and so on.

One time Loki watched Harry Potter, he became very interested in the film, he thought the Midgardian had a unique interpretation of how magic worked. In one of the film he saw a reporter who use her magic to make the pen and the paper record by itself. (iydk, it's the Harry Potter the third movie I think, where Harry participate in the competition between 3 magic schools)

Seeing that, Loki had an idea to do the same, it's super cool and he love the aestethic to work with a quill and paper, so he worked with the spell, and after 1 week of try and fail, he finally made it worked.

So everytime he need to note something he will calling his quill and paper, let it to note everything, he kind of interact with it same as Tony interact with his AI.

Imagine it like this:

Fury: "Alright team I need you to go to a mission, one of my agent had comfirm about--"

Loki: "Wait-wait let me grab my note." (Snapping his fingers and summoning his quill and notebook) "Alright what is it?"

Everyone: "..."

Fury frown but countinue his explanation

Loki *whisper to his quill and notebook: "Did you noted everything?"

They're noded

Loki: "Good girls."

Everyone: "..."