Thanks for the answer Delphi developer.
That was almost what I was trying to do. It removed left, right and bottom border but top border still remains. Anyway your approach is useful also (before I didn't understand to select tabPanel as you pointed in screenshot).
Reading forum (this and other pages) I was able to remove borders by:
1. Creating customCSS
.myNoBorderCSS .x-panel-body-default
{
background: #ffffff;
border-color: #ffffff;
color: black;
border-width: 0px;
border-style: solid;
}
2. adding cls in ExtJS-events
function added(sender, container, pos, eOpts)
{
sender.addBodyCls('myNoBorderCSS');
}
I also hide UniPageControl header by:
UniSession.AddJS(Format('%s.items.getAt(0).tabBar.hide();', [PC.JSName]));
All working well except that tab panel height will be too small (= - header height), but that does not disturb me so much.