When you use the Extra field names setting in Ketryx, any field listed there (and with a value, such as a default) will appear in all Ketryx item records where data is present, regardless of the Jira screen association. This is because Extra field names does not allow you to restrict a field to specific item types.
 

To have a custom field appear only for certain item types, use the Custom item fields configuration and associate the field with specific item types under Item fields. This approach allows you to control both the field's editability and its association with item types in Ketryx, avoiding the global behavior of Extra field names. If you want the field to be read-only in Ketryx, set "isEditableInKetryx": false in the custom item fields configuration.

Example:

1. Define the custom field in Custom item fields configuration:

This makes the field available and read-only in Ketryx, but not editable.

2. Associate the field with the Requirement item type in Item fields:

This ensures the field only appears for Requirement (REQ) items in Ketryx.

3. Set the default value in Jira for the "Custom Field Example" field on the Requirement screen. Ketryx will read this value for Requirement items only.

Summary:
By not including the field in Extra field names, you avoid the global behavior where the field would appear for all item types. For item-type-specific control, use Custom item fields configuration and Item fields instead. Please see the following for more information: Custom item fields configuration, Item fields, Extra field names.