How to make a field read only 

When making a custom editor, it is possible to make fields read-only, so users can see the content of a field, and even copy information from it, but they may not change its content.

From the metadata editor designer, select the field(s) that should be made read-only and open the Item properties panel on the left.

Then uncheck the checkbox for the Allow to edit property.

Now, when a user opens the metadata editor, the field(s) will expose their metadata content, but the user will not be able to make changes.