they have to be in the skinning tab
but in the new update its look like this
before update :

First, I'd suggest that you reduce the amount of currencies you're tracking as that's what's causing your bag to become so wide. As for the skins appearing in the Recent Items section instead of the Skinning one, that's completely expected behavior for items that were recently added to the bag. If you want to force these items to be sorted to their respective sections, simply click the Recent Items section header (the text itself is a button).