Hummmm
<newbie-mode>
Firefox hides the scrollbar when not in use, and the lines aligned to the box looked like it wasn’t scrollable.
Forgive me for your time loss. I’ll provide more - correct - examples.
</newbie-mode>
<frontend-developer-mode>
I’d suggest adding a scrolling shadow, showing a shadow on the top when there is more content on the top and on the bottom when there is more on the bottom.
It comes from a CSS guru, Lea Verou Pure CSS scrolling shadows with background-attachment: local • Lea Verou
I also added the horizontal version and generated a couple of CSS classes I use on the sites I develop: https://codepen.io/massic80/pen/jOQWxNm
This way, anyone would notice there is something hidden under the bottom of the box.
</frontend-developer-mode>
I’d add the same solution to the “Add” menu, since one can’t know that there is something more when scrolling (e.g. RPP)
A shadow on the bottom, with the classes I added above (which don’t show anything if not needed), would help user experience a lot.