GridGroup (source) is as widget group that arranges multiple widgets into grid. Item size and spacing can be specified in constructors. GridGroup is available since VisUI 0.7.2

GridGroup group = new GridGroup(64, 4); //item size 64px, spacing 4px
group.addActor(actor1)
group.addActor(actor2)
//...

Grid group can be embedded in scroll pane. However in such case scrolling in X direction must be disabled.

VisScrollPane scrollPane = new VisScrollPane(group);
scrollPane.setScrollingDisabled(true, false); //disable X scrolling