My mother, grandmother and aunts had a rule that no one was allowed to sit in the seat at the head of the table that was previously occupied by their (now) deceased husbands. They said that this was in accordance with respecting one's parents. (I.e. their children were not allowed to sit in those seats. By extension, they reasoned that if their own kids couldn't sit in the seat, any non-direct family member was forbidden to this, also.)
I know that one must respect their parents even after their death. However, does this respect apply to not sitting in their seat as well? If this is not halacha, is there any source that lists this as a common minhag?