You would like to change the field identified as your "Category" field for a catalogue, but it's not possible because it's grayed out:
This is because the "Category" field is not modifiable when active channels are connected to the catalogue.
 This safety feature is in place because any change will affect the categorization of all these channels.
In order to modify this field, you must deactivate all channels based on this catalogue.
You will then be able to make the modification before you reactivate the channels.
