When can evernote set over 2 layers stacks for notebooks?

[Fren 0]

Hello evernote and everyone,

I started using evernote about 5 years ago.

It is really good to use and I think it is the best personal knowledge management software

But just one thing still bothering me now.

When can evernote set over 2 layers stacks for notebooks? Like file manager?

ex.

Stack1

-------Stack2(Also Notebook)

--------------Stack3(Also Notebook)

---------------------Stack4(Also Notebook)

Evernote is very good, but If I can set more layers for notebooks, it will just be perfect for me.

I'm just wondering why evernote didn't(can't) do this?

It's a question that I want to ask since 5 years ago.

Thank you.