Ability to remember last expanded status

In general use, this could be seen as a trivial thing.
but I think this is a vital feature.
Let me show you an example explaining why this feature is so important.

One day I want to expand certain rem which descendants are about 21463 in its hierarchy. that is the heavy rem (don’t know until I opened up)
despite its unknown heavy hierarchy, I expand all the rem using ⌘ + Shift + ⇩ and get in trouble (too heavy lags).

I think this is covered Make folding be different from hiding?