Create dump file using Oracle SQL Developer
As far as I know, Import/Export and Data Pump are command-line-only types of tools.  But if you really wanted to use that functionality from within SQL Developer (or SQL Plus), Data Pump uses the built-in DBMS_DATAPUMP and DBMS_METADATA packages.  You should be able to call those packages directly, so I would start there.  There's documentation available in the 
Oracle® Database PL/SQL Packages and Types Reference on both of them (DBMS_METADATA and DBMS_DATAPUMP).