Prenab,

I don't know of any in0built field in P6 that tells you that any particular activity is "level4" or "level7" of the WBS hierarchy.

If I was tasked with presenting this, I would generate an activity Number UDF field, an use Excel to generate a value that would be imported back into the schedule to present. But you need to do this each time new activities were generated or if the WBS structure was changed.

do you mean in the gantt area where the bars are ?

if so in the gannt area rigth click bars 

look for current bar labels and highlight it 

then click on the bars label tab 

on the bottom click Add

then select the position that you want it on the bar

under label select wbs path 

or go to current bar 

click on bar labels 

then click on the bars label tab 

on the bottom click Add

then select the position that you want it on the bar

under label select wbs path 

if you are putting it under the bar make sure that the row hight is large enough to see it

if you are looking to band the wbs in the gantt area that is not possible 

Try these:

1) Iin Group and Sort Options - for the WBS grouping you are using, tick the box to "Show ID/Code"

2) In Columns, show the "WBS Path" column