Create tree view in the angular and add two buttons add and sub

Question

Hi,
I have created a tree structure in the angular.  as per my requirement, need to add two buttons that is ADD and SUB in the node.

EXAMPLE:

 > CSS

 >Img  

       >bg.jpg

       >logo.png

      >avatar.png

>js

>index.html

here,  i have 4 nodes, when i clicked the add button against of Img node, the another node should be added in the main tree. that is Img_clone and comes all the files . 
like 

> CSS

 >Img  

       >bg.jpg

       >logo.png

      >avatar.png

>js

>index.html 

>Img_clone

       >bg.jpg

       >logo.png

      >avatar.png