This is tedious, but I'm a firm believer in doing it.
If you're pre-Millennial the below may look familiar. These are sentences that have been diagrammed-- broken down to the most basic components (who did what-- Boys (subject) like (verb) games (direct object). Maybe they stopped having kids diagram sentences because they thought it was a useless exercise, but I always liked it and found it helpful.
Chloe + Yess go to SAE party. Left: C sees Will. Sees C and his girlfriend. Right: SAE house. How calm she stays.
After I write a book, I always diagram the plot in at least one way. It is somewhat tedious but EXTREMELY useful. I diagram every single scene this way, which makes it really obvious to discover when I have extraneous scenes. Plot points go on the left of a notecard or post-it. A line is drawn down the center, and everything on the right is information that is probably needed to be somewhere in the book, but that technically does not move the plot forward.
An example to the left: the major focus of this scene is that Chloe goes to a frat party. Two major plot points occur: she sees Will, and she sees another boy, Charles, with his girlfriend. These things have to happen to move the story forward. To the right are things that need to be somewhere in the book, but not necessarily here (in this case, it works out well that they go here.) A description of the SAE frat house: we need to know what it looks like, but that description isn't part of the plot. (In other words, I would not have a scene that just describes the frat house and does nothing else). The second point is to demonstrate in this scene how Chloe tends to stay really calm even when a normal person wouldn't be. This is a characterization--her tendency to not freak out--not a plot point. It cannot hold up a scene by itself.
Here's another example from a different story:
Left: Team is kidnapped and offered by Riley a second chance to win their stars back. Tank. Right: Base move occurring. NASAR (military) training. Intro Riley
In the above case I color coded blue to indicate the narrator (blue= Dorian). The team is kidnapped and put into a diving tank rapidly filling with water. Obviously that is a clear plot point. Told along the way is an important setting issue--that the entire military base is in the process of planning to be moved to another planet--but technically that information is not a plot point, just something in the background. The packing boxes are laying around, and people are talking about it. Also relevant but not a plot point itself: escaping from the tank brings to Dorian's mind all the training he has endured over the years and how it could be applied to his current problem. Riley is introduced. His introduction itself is not plot--what Riley does is.
When I've had to do serious structural edits, including needing to cut down a book significantly, doing these notecards is really useful. If you have stuff on the right side, but none on the left, this means you can take those things and move them to some other place that actually has plot points. Plot is like the skeleton in the body-- it needs to be there for structure, to literally hold the body up. Everything else can be moved around on the skeleton. I'm of the opinion that there should not be any scenes in a novel that do not move the plot forward. Describing a setting is not plot. Describing a political context is not plot. Characterization is not plot--sometimes it seems like it is, but it should it be. "Bob is an asshole" does not move the plot forward. "Bob gets kicked out of the restaurant (because he is an asshole), getting his wife to realize that she wants a divorce." does move the plot forward.
If I'm doing a multiple POV novel things get a bit more complicated:
Don't bother trying to read this.
On the right: You can see chapter numbers indicated on the left. This is color coded for four different narrators. Each row is one scene, each box colored in indicates one page double-spaced. This gave me a sense of how long each chapter was, how much space each character got, and how much stuff happened plotwise in each scene.
On the right: on the left page is the entirety of a book color coded by POV, with one block of graph paper per each page. The right side is the same thing, for the next book in the series. The width is the same for each. The second book stays with narrators for longer segments of time (I switched to only one narrator per chapter for thematic reasons). This gave me a sense of the "shape" of the book, who was getting long segments and where (sometimes this needed to be rebalanced.)