Once you hit a certain point in your progress in the game called Satisfactory you find yourself in need of a way to track things outside of the game. The game gives you several tools such as the equipment codex and the mathematics calculator feature and the To Do list and the Notes sidebar but those can only carry you so far. You’ll see jokes online about how you’re not a real Satisfactory player until you start making spreadsheets and… well, that’s not wrong, honestly.
Maybe just not in the way you might think.

Let’s get into the note-taking aspect, the part of the game you engage with outside of the game.
Perhaps first one should determine one’s level of “purist” when it comes to the gameplay. This will expand or limit the tools at your disposal. I’m mostly going to cover the toolset I’m comfortable with, your mileage may vary, please pick and choose what works best for you, et cetera et cetera.
A true purist would, I suppose, not use any of the available online tools, relying instead solely on the experience and knowledge provided in-game. That’s a valid choice but I believe that you’ll still need a way to track information and perform more advanced math calculations. I use two specific tools for these tasks:
Obsidian
I used to keep text files, just one or two dedicated to this specific game but also various other files strewn around my hard drive with other notes jotted down (metaphorically speaking). Now? I use Obsidian. I have a main vault within which is a “Gamestuff” folder, and inside of that there’s a document for Satisfactory.
(Honestly, I should have a Satisfactory folder and break out the contents of that one file into discrete documents. A project for another day, I suppose.)
Anyway. Now instead of purely plan text files, I have Markdown formatting available. Highlighting, bullet pointing, section headering, task listing, all of that is at my fingertips to keep my information organized. This is working out even better than the PmWiki page I set up on my webserver ages ago. What kind of stuff am I tracking? Some technical notes (like keeping VSync turned off until the dev team fixes a performance issue related thereto), my TODO list, tracking all the hard drive “alt recipe” results I’ve received so far, the hex codes of various color swatches I use for customization of machinery/etc, beam heights & positions for building “power bars” around lines of machinery, the instructions for the “Rxckxt Roundabout,” and so on and so on.

I’m not paying for the sync service (yet, and in the meantime my vault is included in my daily cloud backup service selections because everyone should be doing backups) but since I don’t access these files from other devices that’s just fine.
Spreadsheet
I use Excel (paid for by my employers), you can use whatever you like, the point being that you will need something that juggles numbers for you. Plug in the per-minute inputs required by a given piece of machinery and use that to figure out how much production you need. Do the math on how many Steel Beams you need to make a particular Space Elevator part and use that info to decide if you’re producing enough. Tally up all of the Encased Industrial Beams you make at your various factories, subtract from that what’s in use by existing factory processes, thus confirming whether or not you have enough surplus to take on another project without expanding production.
I also use it to track trains, of course.

If you don’t know what’s being acquired from or delivered to each platform of each train station, you’re going to get yourself into logistical trouble sooner or later. Ask me how I know! What’s more, having a list of stations and what goes into and out of each platform position helps plan future train stations so you don’t end up with four trains all delivering different products to one location but all of their materials are in the front-most car… whoops!
Now, I could probably have done the train tracking in Obsidian but with a spreadsheet I can auto-update the names in the train itineraries if I update them on the left side (I do change station names sometimes), and I get the color coding as a bonus. It’s just nicer this way.
And that covers the local, on-computer tools with which I keep my Satisfactory experience as streamlined and organized as it is. (Which… may not be saying much, admittedly.)
Let’s talk about online tools. This is where you have to throw out any notion of being a purist about the game experience.
The Official Wiki
Formerly on a Fandom site (ugh), satisfactory.wiki.gg is the new address for the officially sanctioned (but fan maintained) game wiki. Every individual item and game element has a page, along with a few general concepts. I mainly use it for two key pieces of information: What all does Item X get used for, and what are the other ways (if any) to produce Item X? There’s also a fuel usage breakdown, which is useful since the game itself is… not great about showing you how many Fuel Generators you can feed off of a given per-minute rate of fuel production.
Satisfactory Calculator
For years, “SCIM” was the primary go-to site for two things: Planning factory builds, and seeing where everything is on the game map. I do my build-planning elsewhere (more on that, shortly) but having that birds-eye view (orbiting satellite view, maybe?) of all the nodes and collectables can be a godsend.
But it’s definitely “outside knowledge” that you don’t get right away in the game. It’s a way to circumvent the issue of figuring out where to build next by knowing in advance where all the goodies are that you’ll need. Of all the options, this one’s the most like cheating… especially since you can also load a game’s save file into the website and make changes, then re-save the file and use it in your game.

Do with this what you will. I don’t like the idea of editing my save file, but I think that trying to find all the nodes, pods, and alien bits the hard way is the most tedious part of the game so I’m happy to use the… let’s call it “extra aerial survey data” to ease that aspect.
Satisfactory Tools
While SCIM used to also be the go-to for factory workflow planning, my preferred site for that aspect is now Satisfactory Tools. The basic idea’s simple: Tell it what you want to make and how many, it’ll try to come up with the most efficient way to do so, from raw materials through intermediary products and up to your intended output.
(Note: That link is to the 1.0 production page, since up until recently the main page tended to drop you into Early Access mode. If this link breaks… please, someone tell me!)
You can toggle checkboxes for your acquired alternate recipes, and you can even toggle off individual basic recipes if you have your heart set on a particular recipe choice regardless of whether it’s the most efficient option. This might have to do with your available existing production lines, or whatever. It’s up to you.
The site lets you indicate which materials you’re already making, which is handy for cutting down on the complexity of the flowchart if nothing else.

I don’t always try to get exact numbers out of Tools. Mostly what I want to know is the actual flow of things, this to the next thing to the other thing to the final product. None of this does anything I couldn’t work out for myself given enough time and fussing and fiddling, but why fuss and fiddle so much if you don’t have to?
And that’s pretty much that. Design ideas and such I’ll get from a Discord group or a YouTube video here and there, but those are incidentals. The meat & potatoes of getting through my Satisfactory sessions is handled by these tools right here. I hope one or more of them will serve you just as well.