Originally Posted by HarryT
To clarify that last point, in order to save your work you need to copy the "LastFile" folder out out of the BD folder. BD overwrites it whenever you load a different book. What I do myself is to copy the entire "LastFile" folder into the folder containing the source files for the book I'm workin on (I have one folder per book). When I next want to work on the book, I just go to the "LastFile" folder and double click the ".html0" file.
Rather than copy the folder I use the "Make BD File" option (Cntl F11) to save a copy of the workfile. I do this after editing and before ebook generation.