Does 'jemdoc' support multi-level directory on the left sidebar?

[QwertyJack]

I find that there is only a 2-level directory on the left sidebar.
Can I use multi-level, such as a 3-level directory?

In another words, now the left sidebar looks like:

HEAD 1 level 1
    Head 1.1 level 2
    Head 1.2 level 2
HEAD 2 level 1
    Head 2.1 level 2
...

What I want is:

HEAD 1 level 1
    Head 1.1 level 2
        head 1.1.1 level 3
        head 1.1.2 level 3
    Head 1.2 level 2
...

Thanks in advance.

[MengGuo]

Maybe you could contribute then.