If books are in a true INDB file, endnotes or footnotes only work in the first chapter; endnote or footnote links in subsequent chapters need to be created manually. This is tedious, error-prone, and yet bi-directional linking is a requirement for virtually all EPUB companies at this point. Academic books are far too long and complicated to be created in a single file.

Agreed. Even like a "footnote style" (like could it be included in "workspace"?), or if it would work as an "object style" type thing, where we could save the footnote dialogue options & layout tabs info and apply it to each book document?

The "restart every section" is useless when sections are spread across multiple chapters (documents). In this book I'm editing I got it in 46 indesign docs ("chapters") so putting each into a template would be a ton of extra work. Rn I have to go through each of the 46 chapters and put in the same settings for footnotes. So much room for design error and needs to be automated.

There are articles for workarounds using an extra text flow frame on a different Master page, which at least removes room for design errors by not having to "set" the layout every time, but then I'd have to go paste all the footnotes into a single doc and even then it won't reflow across docs or chapters in a book. If there are articles about ways to do footnotes other than ID features, that means ID should do better because publishers are having to do workarounds to use your product effectively.

Same here. My book contains 27 files... I just found out that the endnote features is a very handy feature for my book, and after finishing all the configuration I had to do manually in each of the files...