In an opened KeyStore window, select the key pair entry and click on the right mouse button. From the popup menu select Export > Export Key Pair action. The Key Pair will be exported in the selected file. The Key Pair can be exported in PKCS #12 KeyStore Files format. Also, a PKCS #12 password is required. While exporting a Key Pair, an error might occur if the password length is too long - this has to do with the out of the box Java Cryptography Extension (JCE) limited Strength Jurisdiction Policy Files.

A screenshot for the export Key Pair action is depicted below: