If you are talking about Capacity Planning Overciew
then you are limited to the fields the system data provider has
In this case it is not an object and you cannot add custom fields to that.
I do not know if you can add custom fields to it by adding them to the underlying object.
Firstly you would have to identify the object. Secondly it can be that only the predefined fields from the underlying object are taken into the system data provider.
If you go to configure and List Filter Section you have Primary role available for filtering.
However, the asterisk next to Resource OBS indicates that to be required. You could choose and OBS which contains all and create one if you really need it if there is none.