You could merge schemas, object classes and attribute types from one
schema project to another using the Merge Schemas wizard.
To start the wizard choose
Import >
Merge Schemas from other Projects
from the context menu of the Schema view.
The following wizard appears:

Check each schema, object class and/or attribute type from to merge to the current schema project and click on the Next button.
The second wizard page appears:

Select merge options.
| Option | Description | Default |
|---|---|---|
| Replace unknown syntax | If checked, unknown syntaxes are replaced by Directory String syntax, and appropriate matching rules (caseIgnoreMatch, caseIgnoreSubstringsMatch) are set. | checked |
| Merge dependencies | If checked, dependent schema elements (super classes, super attribute types, may and must attributes) are also merged. | checked |
| Merge inherited attributes | If checked, must and may attributes that are not defined in the class hierarchy in the target schema are added to the merged object class. | checked |