I put smaller items into clear bags and my experience has been that if the security personnel can turn the bag and easily see what's in it, they haven't opened it. They did remove the bags from the backpack (after the first time, I just removed them myself as they checked the person ahead of me). My last visit was September 2018.
I usually only have 1-2 clear zipper bags (like pencil cases if that makes sense), and they aren't packed full (one is usually sharpies and index cards for autographs and the other one is a few diapers and wipes so the diapers aren't soaked in the event of a downpour). Sometimes I have one more small bag with "first aid" items (chafing powder/ band aid/ ibuprofen).
One CM at MK looked at the bags and exclaimed "you're a pro! You came ready today! This is great!" Overall I try to bring as little as possible into the parks to begin with. Now, that isn't to say they don't ever open the bags or won't start opening the bags so YMMV.