You have to do this at the object level. Go to Designer --> Object Designer --> Request Managment and select the main object for which you want this data to show (in your example click on the main level of Assignment). On the right side where the properties are shown you will see a section towards the bottom called "User Interface Properties". To get data to show, choose the Tree Node Description Attributes and open that. In there you will see all the options you can select. This is where you would choose to show your Assigned User, Group, Creation Data, etc...
Also, if you are going to have multiple items that show, the "Tree Node Title Separator" and you can put anything in here you want to separate the attributes. Normally I will use a space | space to separate these.
You can do this for any object collection you want (Notes, Resolutions, Assignments, Tasks, etc...)
Hope this helps.
Excellent! Now you can do this for any of those collection folders you have.