@TinaTian ,
There is a workaround published in the Internet:
1. Select all the actions of the flow, then Edit | Copy or Ctrl+C.
2. Paste them into a text editor of your choice, e.g. Notepad
3. In PAD, create a new empty flow.
4. Copy the content of the notepad done in step 2, then in PAD, Edit | Paste.
Apparently all the actions and variables will be automatically pasted.... But is it really a solution??