How can i change the row hierarchy symbols with downward to plus symbol

Hello, Naidu, 
 
Thank you for reaching out to us. 
 
We recommend you to redefine CSS styles by changing the content property of the icon :before pseudo-element and other properties such as color. 
Please see an example we have prepared for you. 
 
We hope it helps. 
 
Best regards, 
WebDataRocks Team