[2023] "known" Schematics and how to know what you know

The small icon in the corner if the item's box- Tells you information about the item. A gear means it's a weapon/armor with mods in it; Two gears means it's a mod that can be equipped to an item of some sort.. An explosive icon shows an explosive, etc; For recipe books, the icon is a book that is either closed to show you haven't read it, or open to show you have.

https://steamcommunity.com/sharedfiles/filedetails/?id=2984279160
In this example, I haven't read the gas can recipe, but I have read the oil recipe- The other items continuing down the row are showing other items with those little info tags; A pickaxe with mods in it, a tool mod, a building object with shape options, an explosive, an ammo box that can be opened, a material stack that can be unpacked, and a dye that can be used to dye things.