How to create Nested Lists while defining custom attributes?

Yes, but let me know the steps to create such enumerations.

Process Customization is explained in https://jazz.net/library/article/1093 Lab3.

You would create enumeration literals and make the name appear nested e.g.
Batch
Business Process
Cognos Reports
Cognos Reports - Data
Cognos Reports - Enhancement
Cognos Reports - Training

Another approach would be to use two attributes and enumerations and have a dependent enumeration configured to set the second enumeration. Also see Lab4 in the link above.

Thanks for the response.

Here I have a question, if we are going for dependent enumeration is it possible to display and select the value for second attribute only when "Cognos Reports" is selected in first attribute. Please comment

correct.. that is the function of the dependent enumeration.  select from the 1st list, then get a second list customized to the first list.

create all your enumerations with all the potential values.  then create the dependent enumeration definition.. order the enumerations (more than 1 level is supported, I have build one at 4 levels), then select the controlling value, and all the values of the next that apply.
repeat..
note that the second level can overlap.
one last step is when u define the attribute in the workitem that USES these enums is to specify the dependent definition and the depends on value in the listbox of the attribute definition

Hi,

Thank u for the response, I have tried the same but I am having some issue over here that is when I select a value in first enumeration the corresponding values are displayed in the dependent enumeration ,but when I am selecting some other value in the first enumeration then I am getting red bubble beside of dependent enumeration with a message "The selected Value is not applicable" with the previous value selected in the dependent enumeration including the dependent values selected in the first enumeration that is selected for the second time.

Please let me know your response.

Thanks,

anitha

This is to  be expected, the dependent enumeration tells you that the value already select does not match the rules after changing the value it depends on. A user has to select a valid value. 

As Ralph mentioned this is how the RTC function works. it does NOT reset the downstream values when you change something above it.