Please, Oh Please!!!!! Why is there not the capacity to have a book-wide variables list? That is, why not have variables contained/defined in the Book file. When working with very large books comprised of many chapter files, having the variables list defined on a chapter file basis is a giant PITA! If I want to add or modify or remove a variable on a book-wide basis, I have to go through 20+ chapter files. It is SO VERY EASY to get chapter files in a book out of sync variable wise. Over the course of years, and half a dozen revisions, and multiple authors touching each chapter file, the variables lists become a freaking MESS! Old, residual junk in one file, not in another. Variable definitions changed in one file but not in another.
There MUST be a way! (I can think of several - like have a variables list in each file, but if you are working with a book, create a composite/master list from each file in the book and attach it to the book file). Not rocket science.
This file-by-file variable list business is a really Enthusiasm-for-FrameMaker Killer.
(Does anybody from Adobe even read these comments?)