Current state:

If a portallayout receives a height (either calculated with vlfex, or through height), and one of the portalchildren contains enough content to go over the size of the portallayout, then the rest of the panels are displayed outside of the portallayout viewport.

Standard behavior for kanban seem to be that individual columns can be scrolled without affecting the rest of the UI, so this would require scrolling the portalchildren-content nodes.

the following sample provide a reasonable POC for this behavior:

<style>
.z-portallayout-vertical>.z-portalchildren {
 padding-bottom: 25px;
}
.z-portalchildren-content {
 overflow-y: auto;
}
</style>