Using dynamic variables in queries

Have you checked this?

To answer your question: yes it is possible. But even better, take the Simple Query as is and place it into an Advanced Query syntax (<query) and now you can give it a title and so on. I have done this with all my simple queries:

#+BEGIN_QUERY
{
:title [:h2 "Morning Routine:"]
:query (and [[Morning Routine]] <%today%>)
}
#+END_QUERY

Hope it helps.