Is it possible to set the height of groups (owners) individually or do all owner rows always get resized together and stay the same height?
No, you cannot set the height of any one row individually; the height of all rows is determined by the amount of vertical space available divided by the number of rows.
Is there any option to determine the row height ?
So it is possible to implement a scrollbar but it wil not be used until the user resizes the rowheight?