If there is no image brightness difference between adjacent structures then you need to provide a lot of scribbles for “Grow from seeds” to get a nice result. In this case, it may be better to use “Fill between slices”.
“Fill between slices” is only applied to the currently visible segments, so you can exclude any segments by hiding them. You may need to enable segments to overlapping (Modify other segments → Allow overlap or Overwrite visible) to prevent overwriting of hidden segments.