I have not seen a copy function for editors in the UI.  The only way I have found to make a copy of an editor is in the XML - i.e. the "Process Configuration Source".  There are 7 sections to update.  You would need to identify the target editor to copy, find its definition in each section, copy and replicate that XML source and change the id of that XML entity to a unique id for your new editor.

The first time you do this it may take more time than creating a new one from scratch in the UI.

And, XML source is very unforgiving with typos or any errors, one bad character and nothing works.

1. Work Item Types - id="com.ibm.team.workitem.configuration.workItemTypes"

    define work item - <type category="com.ibm.team.workitem.workItemType" icon="processattachment:/workitemtype/bug.gif" id="defect" name="Defect">

2. Editor Presentation Bindings - id="com.ibm.team.workitem.editor.configuration.workitemTypeEditorIdBinding"

    standard editor - <workitemTypeEditorIdBinding editorId="com.ibm.team.workitem.editor.default" workitemType="defect"/>
    plan preview editor - <workitemTypeEditorIdBinding editorId="com.ibm.team.apt.planPreview.default" target="com.ibm.team.apt.ui.internal.previewPane" workitemType="defect"/>
    web inline editor - <workitemTypeEditorIdBinding editorId="com.ibm.team.workitem.web.inline.default" target="com.ibm.team.workitem.web.inline" workitemType="defect"/>
    light weight editor - <workitemTypeEditorIdBinding editorId="com.ibm.team.workitem.lightweight.editor.section" target="com.ibm.team.workitem.editor.lightweight" workitemType="defect"/>

3. Editor Presentations - id="com.ibm.team.workitem.editor.configuration.presentations"

    plan preview tab - <tab tabId="com.ibm.team.apt.planPreview.default" title="Default"/>
    web inline tab - <tab tabId="com.ibm.team.workitem.web.inline.default" title="Default"/>
    editor definition - <editor id="com.ibm.team.workitem.editor.default">
        start with editor definition, find each piece by id
            editor defines the tabs
            tabs define the sections
            sections define the presentations
            tabs and sections can be, and are, reused
            do not reuse tab/section if you want to make changes
            create a unique one with a unique id that is only connected to new editor

4. Workflow Binding - id="com.ibm.team.workitem.configuration.workflowBinding"

    define binding - <workItemCategoryBinding workItemCategoryId="com.ibm.team.workitem.workItemType" workflowId="com.ibm.team.workitem.defectWorkflow"/>

5. Workflows - id="com.ibm.team.workitem.configuration.workflow"

    define workflow - id="com.ibm.team.workitem.defectWorkflow"

6. Team Permissions

    define permissions (if required)

7. Team Behavior

    define behaviors (if required)