We are using synonyms for a number of objects in our database, but SQL Developer 4.0.2 seems to be unable to resolve these when trying to ctrl-click to open the declaration.
What does 'unable to resolve' mean? You mean there is nothing on the 'Details' tab?
Is the DDL listed on the 'SQL' tab?
I do have one synonym in the SCOTT schema that displays no details. That one is on a non-existent object:
CREATE OR REPLACE SYNONYM "SCOTT"."TEST_SYNONYM" FOR "SCOTT"."ABCDEF_JUNK";
The 'details' display for all other synonyms; just not for those based on non-existent objects.