Just for my note, I want to change the Default Application Creation Directory while clicking 'New Application' menu in Application Navigator in JDeveloper.
Edit Applications.xml file at C:\Users\user\AppData\Roaming\JDeveloper\system12.2.1.4.42.190911.2248\o.jdeveloper like below.
Update <workDirectory path> with your desired directory.
<?xml version = '1.0' encoding = 'UTF-8'?>
<system nselem="system" class="oracle.ide.model.IdeSystem" xmlns="http://xmlns.oracle.com/jdeveloper/110000system">
<listOfChildren class="oracle.ide.model.DataList">
<Item class="oracle.ide.model.Workspaces">
<activeProjectMap class="java.util.HashMap"/>
<activeWorkspaceURL/>
<listOfChildren class="oracle.ide.model.DataList"/>
<workDirectory path="/D:/JDeveloper/mywork/12.2.1.4/"/>
</Item>
<Item class="oracle.ide.model.Connections"/>
</listOfChildren>
<preferences>
<preferencesMap class="java.util.HashMap">
<Item>
<Key>DefaultProject</Key>
<Value class="java.net.URL" path="DefaultWorkspace/Project1.jpr"/>
</Item>
<Item>
<Key>DefaultWorkspace</Key>
<Value class="java.net.URL" path="DefaultWorkspace/DefaultWorkspace.jws"/>
</Item>
</preferencesMap>
</preferences>
</system>