- allow embedding of fonts
- create multiple document sections
You would not believe just how many of us keep Lotus WordPro around and use it for production writing despite the fact it hasn't been published since IBM killed OS/2.
This wasn't just multiple sections. You could tag which section would be included for printing, re-arrange entire chapters by dragging their section to a new spot on the list.
This functionality allows an author to keep their research, to-do notes, cut pile, and everything else in a single file. When you can embed fonts in the file the next computer to open the file will have the correct fonts no matter what OS.
This is your proprietary file system so you can write the rules.
Professional writers have been dying for something to be both reasonably priced and on par with Lotus WordPro.
You really want to get SmartSuite 9.8 to understand just how powerful the total package was.
Do not know if I would trust this link, but that is why one has sacrificial machines off the company network with really good virus scanners.
There are various people selling physical copies on eBay. Just be sure you get a CD version unless you still have a functioning floppy drive.

You may never be able to find the actual LWP specification, but you can implement the features in your own format.
This place might be able to help you.