I have electric heat with heat pump each major room has cold air returns near floor and 1 near the ceiling. Which 1 should be open and which 1closed during the winter heating season

It all depends upon weather or not the return airs were designed to be blocked seasonally or if they should be left open all year.

Usually you close the top during the heat season to force the lower cold air back to the furnace and the reverse in the summer by closing the bottom to force the unit to draw in warm air in the summer. But the big question is was your system really designed to utilize this or are they supposed to both be left open all the time. To little return air can have damaging consequences to the equipment.

There is no way I can tell from here how your system is designed or if your system meets the minimum return air requirements with all the lower OR higher return airs closed off as in for seasonal use. Just giving you all the facts.