I have drafted the chapter on building transactions:
https://github.com/libbitcoin/libbitcoin/wiki/Building-Transactions
Feedback welcome! I feel it is developing a bit in the direction of: Bitcoin + Libbitcoin doc, but maybe that's ok or a good thing.
Next: Slicing previous chapters into smaller ones. Other topics: P2SH/Segwit/Stealth Addresses ... moving examples into tests(once I revise the earlier chapters).