[feat] Scroll bar on action lists

[VaticanUK]

Is your feature request related to a problem? Please describe.
I believed that actions were missing from the actions lists because there is no visual indication that these lists are scrollable (see bug #554)

Describe the solution you'd like
Some sort of visual indication that these lists are scrollable - a scroll bar, an arrow at the bottom of the list, something along these lines

Describe alternatives you've considered
There aren't really any alternatives - the fact that there are more actions is not currently easily discoverable to users

Additional context
see #554