This Burp extension adds an item to the context menu - when right-clicking in the request in Proxy or Repeater - to copy the entire "Cookie" header without having to manually select it and press Ctrl+C. It's useful for me when updating session information of tabs in the Repeater for saved projects.

copy_cookie_header.py

from burp import IBurpExtender
from burp import IContextMenuFactory, IContextMenuInvocation
from java.awt import Toolkit
from java.awt.datatransfer import StringSelection
from javax.swing import JMenuItem

class BurpExtender(IBurpExtender, IContextMenuFactory):
  
  def registerExtenderCallbacks(self, callbacks):
    self.helpers = callbacks.getHelpers()
    callbacks.setExtensionName('Copy "Cookie" header')
    callbacks.registerContextMenuFactory(self)

  def createMenuItems(self, invocation):
    context = invocation.getInvocationContext()
    cookie_header = self.getCookieHeader(invocation)
    if context == IContextMenuInvocation.CONTEXT_MESSAGE_EDITOR_REQUEST \
    or context == IContextMenuInvocation.CONTEXT_MESSAGE_VIEWER_REQUEST \
    and cookie_header != None:
      label = 'Copy "Cookie" header'
      menuItem = JMenuItem(label, actionPerformed=self.copyCookieHeader)
      menuItem.putClientProperty('cookie_header', cookie_header)
      return [menuItem]

  def getCookieHeader(self, invocation):
    request = invocation.getSelectedMessages()[0].getRequest()
    headers = self.helpers.analyzeRequest(request).getHeaders()
    for header in headers:
      if header.startswith('Cookie:'):
        return header
    return None

  def copyCookieHeader(self, event):
    menuItem = event.getSource()
    cookie_header = menuItem.getClientProperty('cookie_header')
    clipboard = Toolkit.getDefaultToolkit().getSystemClipboard()
    clipboard.setContents(StringSelection(cookie_header), None)