The ASN.1 Editor tab can be used to edit an ASN.1 schema.

The tab itself can contain multiple tabs, one for each schema file being edited. To edit a schema file, either a new schema file must be created (via New -> Schema... in the File menu), an existing schema file must be opened for editing (via Open Schema... in the File menu), or by double-clicking a previously loaded schema file in the Project View.

Once the schema file has been edited as desired, it can be saved through the File menu. In order to use the schema with an ASN.1 data file, it must be validated (using the Validate schema option in the Tools menu).