CJW

I'm a long time user of ID and while there were many things I did not like about it, its tool tab management was really efficient. The pop out and non-overlapping settings tabs were clean and easy. By comparison, I find that my tabs jostle for space and are always present (I am not aware of a way of shrinking them to a simple icon). 
It is not difficult to do, so I'm guessing it is a conscious choice not to implement?

There is no loss in functionality or global editing with the book features in InDesign. It allows one to manage a project effectively. As a book grows, single file editing becomes less viable. It is inconceivable to edit a 600 page fully illustrated book as one file.
Affinity has made great strides across their applications, they just need to let the community know if this is a temporary, accidental or deliberate miss.

Just for perspective, removing the rose-tinted glasses.  Adobe ID started off pretty shaky in a world dominated by Quark - I have been using ID since the beginning and PageMaker before it. ID's Pagemaker import feature was useless and that was from the PageMaker version that Adobe made after they bought from Aldus. The layout, tables, typography and stability were all over the place. In the end, I gave up and restarted. It reinforces the practice to keep the resources close to hand.  I currently have two 300+page books in CS6 and hope to abandon ID as OSX ditches support for 32-bit apps.
A bigger concern for me is the support of large documents - the ID book feature was very useful for management.

Just for perspective, removing the rose-tinted glasses.  Adobe ID started off pretty shaky in a world dominated by Quark - I have been using ID since the beginning and PageMaker before it. ID's Pagemaker import feature was useless and that was from the PageMaker version that Adobe made after they bought from Aldus. The layout, tables, typography and stability were all over the place. In the end, I gave up and restarted. It reinforces the practice to keep the resources close to hand.  I currently have two 300+page books in CS6 and hope to abandon ID as OSX ditches support for 32-bit apps.
A bigger concern for me is the support of large documents - the ID book feature was very useful for management.