This would definitely be a nice feature to have. This is a little late, but here is a quick and dirty CSS workaround for a vertical orientation on the left side. Just add the
tabstrip-vertical class to the tabstrip element. It's not perfect, and a better/more robust solution would be appreciated.
.k-widget.k-tabstrip.tabstrip-vertical {
/*Width of the tabs*/
padding-left:12em;
}
.k-widget.k-tabstrip.tabstrip-vertical > ul.k-tabstrip-items {
left:-1px;
position:absolute;
}
.k-widget.k-tabstrip.tabstrip-vertical > ul.k-tabstrip-items > li.k-item {
display:block;
border-radius:4px 0 0 4px;
border-width:1px 0 1px 1px;
/*Width of the tabs*/
width:12em;
}
.k-widget.k-tabstrip.tabstrip-vertical > ul.k-tabstrip-items > li.k-item.k-state-active {
border-right-color:#fff;
border-right-width:1px;
}