Not sure that this is possible, but the docs do have this option, even though I'll have to test if this does what we want or not. The bit about "group list" in the description is what makes me uncertain this option will work.
option name
type
default
description
verticalScroll
Boolean
false
Show a vertical scroll on the side of the group list and link it to the scroll event when zoom is not triggered. Notice that defining this option as true will NOT override horizontalScroll. The scroll event will be vertically ignored, but a vertical scrollbar will be visible
Not sure that this is possible, but the docs do have this option, even though I'll have to test if this does what we want or not. The bit about "group list" in the description is what makes me uncertain this option will work.