How to edit DLP "File Type Include in" field in FortiManager

Hi All

I'm doing some work with DLP in FortiManager and can't work out how to edit file types. From the FW documentation it seems simple, but I see no way to edit the field in FM. Is it just me going mad. I want to be able to create a new sensor with  different file types to the ones defined by default.

I have no direct access to the FW's only via FM.

Thanks in advance