User script providing the functionality discussed at https://jira.atlassian.com/browse/JRA-13079. Provides a link from a JIRA issue page to a search page containing the issue's subtasks, where then can be modified in bulk.

gistfile1.txt

// ==UserScript==
// @name           Jira: Edit all sub-tasks
// @description    Open subtasks of a story in search so they may all be modified at once
// @match         http://jira.your.company.com/browse/*
// ==/UserScript==
 
(function(){
    var matches = location.pathname.match(/[A-Z]+-[0-9]+/),
        list, id, item, link;
 
    if (matches){
        id = matches[0];
 
        list = document.getElementById('subtask-view-options');
        if (list) {
 
            link = document.createElement('a');
                link.href = '/issues/?jql=parent%20%3D%20' + id,
                link.className = 'aui-list-checked aui-list-item-link',
                link.title = 'Show and edit subtasks in navigator',
                link.innerHTML = 'Edit All';
 
            item = document.createElement('li');
                item.className = 'aui-list-item';
                
            list.appendChild(item);
            item.appendChild(link);
        }
    }
})();