I am writing a long story - 20K words, 40 pages. I want to break out chapters to edit separately.
If you want to use separate files for each chapter, please have a look into the manual (available from http://www.libreoffice.org/get-help/documentation/) or wiki on how to use master documents.
Option 1:
You can use only keyboard shortcuts (no need for mouse). Press SHIFT key and hold it down while pressing one of the keys: PageDown, PageUp, Left, Right, Up, Down do select text (it depends what you would like to select). When text is selected you can CTRL+C to copy (or use Copy from tools).
Option 2
Another option if you used Headings styles for chapters:
- View | Navigator
- Click plus at Headings
- Click on chapter from a tree and click on button Demote Chapter or Promote Chapter.
Option 3
Don’t know why would you like to edit each chapter separately… Maybe what you need is using Page styles, in this case look at: How can I ensure that each page is started from the top?
Please write why do you need to edit chapters separately? 40 pages is not a huge document and I would never breake it into master child relationship if not really needed.