Um, I used to do this, a few years ago. Thing is, I was pretty meticulous about it—more than I really needed to be, perhaps.
I had manuals for video games, Lego sets, an electric woks, a digital thermometer, my battery-powered soldering iron, the washing machine, the kitchen table, … I had a lot of manuals, and thus, a lot of binders.
I needed about eight 2” binders (the big ones), and I tried to categorize the manuals so that, if I actually needed a manual, it would only require searching one binder.
I stuffed the manuals into sheet protectors, and didn’t worry about alphabetizing or ordering them in any way, as long as they would go into the right binder.
I no longer use binders. It was too hard to get the right balance of categories. “Electronics.” Is that anything that has a transistor? What if it is a hand-held game… shouldn’t that be in “Games and Toys?” I gave up trying to figure it out.
Also, some manuals (e.g. for the dishwasher or the giant poster-sized manual for some toy) were larger than the plastic sheet protectors. It was very difficult to get them into and back out of the sheet protectors.
What I do now is this: I have a single plastic box I got from Target, with room for a lot of manila folders, just for user manuals, warranties, and original store receipts. Each folder has a very specific type of thing in it, but is labeled with the type of the thing, rather than a brand name.
Let’s say I get a new Canon EOS-1DX DSLR camera (just an example; I don’t have one). First, I will open the box of folders, and see if I have a folder already labeled “Cameras”. If so, I’ll check the contents of that folder to see if any manuals are for cameras I no longer own, and I’ll put those in recycling. If not, I’ll make a new folder called “Cameras” (not “Canon” or “DSLR”) and put the manual in it. I’ll file it alphabetically.
It’s simple, fast, efficient. I spend almost no time thinking about categories, and the folders, unlike the binders, always hold any size manual without effort.