I get that part but from the 2 images i took the cactus has just a normal blue highlight when the bigger image has more of a squiggle highlight style to it which is what i was trying to figure out .When you pick up an item that creates a new stack it will have a highlight around it the first time you open up your inventory. The highlight goes away if you mouse over the item or close and re-open your inventory. There also is an option to turn it off.
Oh, the squiggle highlight is to show you've favorited an item. If you hold left alt when in your inventory you will see your cursor changes to a star, when this is active you can click on anything to favorite it. Favoriting items means you wont quick stack them, deposit all them, quick trash them or quick sell them. You can just hold alt and click on them again to unfavorite themI get that part but from the 2 images i took the cactus has just a normal blue highlight when the bigger image has more of a squiggle highlight style to it which is what i was trying to figure out .