You need to select the static row group that corresponds to your subgroup. In the rows group area, click the dropdown arrow on the left and select 'Advanced Mode'.
Click through the rows under Row Groups until you find the static group that highlights your subtitle. Open the Properties of that group (F4), and set KeepWithGroup to After and RepeatOnNewPage to True.
You need to select the static row group that corresponds to your subgroup. In the rows group area, click the dropdown arrow on the left and select 'Advanced Mode'. Click through the rows under Row Groups until you find the static group that highlights your subtitle. Open the Properties of that group (F4), and set KeepWithGroup to After and RepeatOnNewPage to True.