Interactive filter on additional assignee list

[Raymond Tapper]

Is it possible to create an interactive filter for a report like this?

When I try to create the filter, Additional assignee can't be selected.

[Brian Lancaster]

Can you tell me how these fields are setup? I noticed that you have Group list as well and it looks not to be selectable. These do not appear to be out of the box fields.

[Raymond Tapper]

Here is what I have.
I thought all user created fields were prepended with 'u_' ?

[Brian Lancaster]

Usually that would be correct. I wonder if there is a plugin that add these fields as I have never seen these two fields on the task table.

[Raymond Tapper]

It looks like all the non-selectable options in the interactive filter are list type.