Danke (Thanks in German) .
Replies for your below doubts :
I mean first initial query it will be there in first tab, OK. when the user click on for example engineering row, it should open the tab where I put the bex query for the engineering individual hierarchy report. Got it ? Can we do this ?
When you are using RSBBS functionality to jump from first BEx query to 2nd BEx query, the 2nd bex query will always open in an another excel window. But you can still give the workbook for the first query and tell the user that if he/she does a right click to go to the detailed query it will always open in a new window. This will not be a part of the workbook.
How to do the hierarchy variable for the 2nd query ? and what details to maintain in RSBBS tcode.
For the hierarchy node variable in the second query check the below screenshot to see the properties of the variable highlighted in yellow color.
For the RSBBS settings do the below steps :
1) Go to transaction RSBBS and give your send query i.e. the first BEx query and click on create .
2) Maintain the receiver query i.e. BEx query 2 and click on Assignment details :
3) Maintain the assignment details as shown below. Click Apply and finally save.
Pheww 
.... I hope the above explanation was helpful.
Let me know if you have further doubts.
I would say convince your users for this kind of a report execution.
Regards,
Ashutosh Singh