Complex schemes are often discussed by the big 4 consulting companies (Deloitte, PWC, KPMG, E&Y). They mostly deal with large multinational companies and optimizing for them. If you search for some PDFs on their websites, you may find some surprisingly useful content but it requires more digging.
Thanks for some suggestions; I’ll add those on my watch list
Right now I am looking at
Offshore Banking 101: How to Keep Your Money Safe and Secure in the World's Best Tax Havens
The Law and Practice of Offshore Banking and Finance
Still without success to find anything on international trade and offshore schemes; I am always wondering how those trading companies in Geneva, London, Singapore use offshore companies to minimize taxes, avoid sanctions…