You can edit a part's attributes, properties, and symbols in the component library after it is used in a project. Then update the part(s) in your project.
You cannot edit (change) an internal part number once it is used on a project. You can copy the part (in component library), giving the it the new internal P/N and other changes you desire. Then swap out the part in your project(s).
Hope that helps.
I am unable to edit the number of cavities on a splice... its currently set to 9 and i am unable to place the splice in a diagram because it says pins have not been added to the symbol. Everytime i try to change it to 1 it resets it back to 9.