Cleaning up my old Drupal 7 code that I don't use anymore and don't feel the need of picking it up for a D9 or D10 port. Feel free to ping me if you want to take over this module
In this specific case, Paragraphs clearly won the 'battle', luckily the rules of the game have been changed in releasing full project modules since then ;)
Flexinodes are fieldable entities that can be embedded into a host entity.
The main difference between this project and field_collection is that flexinodes allow a sitebuilder to define more then one fieldable flexinode entity per host field instead and share the flexinode entities between host fields. A true many to many relation between Host entity and flexinode's.
This tiny module enhances the configuration options for the book module.
It gives the chance to set a defauld child for every content type that are set
for book outlines.