Now that I've had my big breakthrough in my Polish line research, I've easily gone back a few generations but records I focused upon and would like very much remain missing or undiscovered. They are yet to be indexed for sure. I've not found that the death records have much to offer in identifying who the dead person was married to. The death records seem to be the least indexed as well.
TO FOCUS and potentially reduce the time spent on looking for records page by page here is what I do.
I look at the marriages of the children. If there have been two - three - four - marriages, I look at the marriages of the children from those marriages too because in these records there is a notation about each partner's heritage. If possible start with the first married child and work forward in time. If it says the parent is p.d. (parent deceased) you'll know that at the date of that wedding, that parent is dead. Or both are.
ie. Jan's marriage 1835 parents both alive
Marianna's marriage 1838 note that her father is diseased
Sophia's marriage 1843 note that both parents are deceased.
Therefore I know that I need to look from 1838 to 1835 for the death of these children's father. And from 1843 to 1838 for the death of these children's mother.