This topic is an inconvenience and obstacle we've heard about from several of our clients. Many people are creating new pages/assets and then expecting to link them to an existing drop-down menu or create a new drop-down menu from the page they just built. Right now, its better to create the drop-down menu you want and then start building the page. However, we understand our clients want the flexibility! The solutions for now are: 1) Add a teaser on the desired page that will link to the asset you've already created. (Quick work-around but not a permanent fix) 2) Copy and paste the content you currently have in one asset, and move that content to the page you can access from the drop-down menu. (Possibly a bit more time consuming but is a permanent fix) We recognize this as a concern and hope to address it shortly!
Addressed in the latest release. :)