Hi @andre,
You can use this method:
lv_obj_set_style_local_border_side(your_table, LV_TABLE_PART_CELL2, LV_STATE_DEFAULT, LV_BORDER_SIDE_FULL);
You can vary the LV_TABLE_PART_XXXX to change different sections of the table.
The LV_BORDER_XXX_XXX defines are in lv_style.h
I hope that helps.
Kind Regards,
Pete