There is a checkbox “Use Part Catalog Description as Description for Inventory Part” under Inventory Part à Inventory Part identification tab which seems just a display of the checkbox for “Use Part Catalog Description as Description for Inventory Part” from the path i.e. Site à Extended Site Info à Inventory à General path for the field.
We are not able to control the checkbox from an Inventory Part à Inventory Part Identification tab for a single part and if we uncheck that checkbox from the Site then the rule is applied for all inventory parts and it allow users to change the text in inventory part description for all parts.
The requirement to change Inventory Part Description for some parts without changing the part description in Part Catalog field and without changing the setup in Site à Extended Site Info à Inventory à General path for the field “Use Part Catalog Description as Description for Inventory Part”.