As far as I know, you'll need to tweak the theme, but for this specific task, it's pretty easy to do. I think this'll work.
- Select the
ItemList
in question
- In the inspector, go to the
Theme
section
- Expand the
Custom Color
item
- Activate the
Guide Color
checkbox
- Open the color selector and slide the alpha value down to
0
, making the separator completely transparent.