If a message is too long, Gmail truncates the content and adds a link at the bottom like so:
[Message clipped] View entire message
If you click on “View entire message” while viewing a Gmail message in the Legend email beta pane, it opens the full message in the pane, but with no way (that I can tell) to get out of that message back to the original message or Inbox. The only ways to get back to the Gmail Inbox is to open an email from an outline pane, or to select “Restore default view” and quit and restart the app.
