Use an External DITA Open Toolkit in Oxygen XML Editor

Oxygen XML Editor comes bundled with a DITA Open Toolkit, located in the [OXYGEN_DIR]/frameworks/dita/DITA-OT directory. Starting with Oxygen XML Editor version 17, if you want to use the external DITA OT for all transformations and validations, you can open the Preferences dialog box and go to the DITA page, where you can specify the DITA OT to be used. Otherwise, to use an external DITA Open Toolkit, follow these steps:

Edit your transformation scenarios and in the Parameters tab change the value for the dita.dir parameter to point to the new directory.
To make changes in the libraries that come with the DITA Open Toolkit and are used by the ANT process, go to the Advanced tab, click the Libraries button and uncheck Allow Oxygen to add high priority libraries to classpath.
If there are also changes in the DTDs and you want to use the new versions for content completion and validation, go to the Oxygen XML Editor preferences in the Document Type Association page, edit the DITA and DITA Map document types and modify the catalog entry in the Catalogs tab to point to the custom catalog file catalog-dita.xml.