Unified Inbox - Filter work items based on Substituted user

Hi All,

I have enabled Unified inbox and working as expected. I have created substitution rule for two employees .

I am getting their  work items into my unified Inbox  since i enabled the substitution for both but I am unable to filter them see which work item is belongs to which user.

Question, can I search the work items based on the substituted user? is there any configuration or filter available to check this functionality?

If have to do custom development , in which view /controller and how to customize it.

Thanks

Krish