Rekordbox track management

Hi I"m Gavin,

I use Rekordbox 5.2.0 with DDJ-RB on PC(win10 x64)

But I got a question about  track management

when I open my folder,the tool will show the tracks at the same layer

but don't show the tracks below the folder

for example,

I have Folder Name:[2012],and it include 3 folder with some tracks like [Trance][EDM][House],and some tracks 

When I Click Folder[1988],It just show those tracks at [2012],and don't show the tracks in [Trance][EDM][House]

But I ask my friend about this,he say that it will show all tracks below the current folder on MBPR.

Maybe I have to change some setting about it, but i can't find it.

Can someone do my a fever,Tell me how can i enable the setting ?

Thanks for your reading,and sorry about my poor English. :p