Hello Bartlomiej Wojdyna,
1. RadPanelBar ListBar style does not support scrolling. The layout in the listbar style is very specific because the Height of the expanded RadPanelBarGroupElement is calculated as follows: the PanelBar Height is substracted from the sum of the caption heights of all RadPanelBarGroupElements. I suggest you use VS2005 or ExplorerBar styles when you need scrolling behavior or you have many RadPanelBarGroupElement instances.
2. If you need to enable the scrolling logic in RadPanelBarGroupElement when the EnableHostControlMode property is true, then you have to set its ContentPanel AutoScroll property to true.
Please feel free to contact us again, in case you need more information.
Sincerely yours,
Boyko Markov
the Telerik team