title: How to move a subtree to another subtree in org-mode emacs
body: <p>I'd like to perform one simple task but there seems to be no clear solution for it:</p>
  
  <p>I have a structure of subtrees like this:</p>
  
  <pre><code>* Tree A
  ** Subtree A1
  ** Subtree A2
  * Tree B
  ** Subtree B1
  ** Subtree B2
  </code></pre>
  
  <p>I'd like to set up one key shortcut to move subtrees from Tree A to Tree B. Moving to the archive seems to be easy, but do you have any clue how to do it within one file? </p>
  
  <p>Any help appreciated! Thanks!</p>