I am not at my computer atm but I think I know what your problem is, its just a little hard to describe from memory.
Under the mod list, the left one, there is a menu with sorting options. I accidently changed this by hovering over it while scrolling the mouse wheel (I believe that's what happened). This sorted some mods into expandable trees and also hindered mods from being dragged and dropped. Change it back and this â€problem" will be fixed.
dreadflopp's post in Can I disable Enhanced Blood Textures (with STEP Extended Patch) was marked as the answer