How to build a tree with the preservation of remote branches?

Question

Database design

You need to build a tree that changes frequently. And I made such a tree using the Nested Set method. But the problem arose when I realized that the old branches of the tree needed to be preserved. Those. if I delete a branch or an individual item, it shouldn't be permanently deleted. There should just be a note about its removal. And when I request a tree, as of a month or a year earlier, the tree that was as of that period should be loaded.

Answer 1

AND?
Another column in the is_deleted table and, accordingly, in the right places in where is_deleted=0
....
upd, more precisely nullable delete_date is better right away - and in the conditions accordingly (delete_date is null or delete_date <= threshold_date)

Answer 2

You can make versioning of one line (there is a lot of this on the network). And for tree versioning, you need to make a copy of the entire structure or block subordination changes.