Also you can use this approach I think.
1. UniContainerPanel
---> UniMemo (align = AlClient)
2.
procedure TMainForm.UniFormCreate(Sender: TObject);
begin
with UniMemo1.JSInterface do
JSAddListener('afterrender', 'function(){this.setStyle("width", "100%");this.setStyle("height", "100%")}');
with UniContainerPanel1.JSInterface do
JSAddListener('afterrender', 'function(){this.initResizable({'+
'dynamic: true,'+
'pinned: true,'+
'handles: "s e se",'+
'heightIncrement: 20,'+
'widthIncrement: 20'+
'})}');
end;