I don't know specifics about folding scissors, but I do know you can't take one of those yarn cutter necklaces with the hidden blades on a plane precisely because of the blades. Scissors with blades under 3.5 or 4 inches are usually allowed, though you might get some side-eye from your agent. I usually pack them right next to my little ruler in case there are questions.
Right at this moment, my current little notions pouch in my purse contains a measuring tape, the clover darning needle case mentioned above with needles inside, some waste yarn and scraps of yarn, a cable needle, small scissors, a button from a LYS, a dpn point protector, and a golf pencil. The supplies inside sometimes change depending on it I need a special tool for my project on the go or if I pick something up while I'm out and about.