is it possible to create new tabs and place them under quick tabs, i.e, i want to create two new quick tabs and add them under (nesting structure) already existing three quick tabs...How can i achieve this
I'm not sure how nested tabs can be created from QuickTabs admin UI. But I believe you can render the child tabs programmatically. The below is how to render a quicktab.
You can add such kind of code snippet into your view/block of a particular parent tab.
Let's say for example, you have a parent tab "Parent Tab 1" which is assigned to a block created from admin/structure/block/add. You could add the above code snippet into the block body.
If you enable the "PHP Filter" module, you can embed any PHP code into the block body when you select "PHP Filter" text format.
Then, when you access the "Parent Tab 1", you will see another quicktabs inside which is printed programamtically.
If I understand your request well, I think this is the solution supplied by @monymirza. But in the latest stable version of quicktabs you have the possibility to select quicktabs to be show under a tab.
Checkout this image to see : (ab is a quicktab instance that has been created earlier, and c is the parent tab that will contain ab)