If you want to add to a row in the repeating panel, you could modify its items.
Try inspecting self.repeating_panel_1.items. It is a list of dictionaries/rows.
If you want to add a data row panel, could you use add_component and rearrange the full component list?
Example,
label=Label(text='put me first')
row=DataRowPanel()
row.add_component(label, column=1)
comps=self.data_grid_1.get_components()
comps.insert(1, row)
self.data_grid_1.clear()
for c in comps:
self.data_grid_1.add_component(c)
I’m not sure if there is another way to do this without having to clear and then re-add components.