|I'm not sure what Pattern Folding School pattern manufacturers learned from, but I can never make sense of how to get those tissue patterns back in the envelope along those fold lines! If you like to store your patterns in the original envelopes like me (small, compact, pretty pictures), you can give your tissue pieces a quick press with a hot, dry iron to get them down to size.
Take all of your unfolded tissue pages and fold them however you like down to a size that will fit the pattern envelope--never mind those pesky factory fold lines!--and quickly press them with an iron set to the "wool" setting. If you'd like to get an even smaller result, press with the iron along each crease that you make. As you use your pattern pieces, do the same with each cut piece and return them to the original envelope. Pressing the pieces gets them down to the right size with very little stress on the original pattern sleeve.
I then store the sleeves in small 6"w x 12"l x 4"d rectangular, linen-lined "Sew Essentials" wicker baskets that I purchase at Jo-Ann Fabrics, usually for 50% off. Each basket will hold approximately 15 patterns. I arrange the patterns by style, gender, or period and place the baskets side-by-side on an open bookshelf... A very attractive way to store and display your patterns!