I held a talk about developing extensions for SAP S/4HANA including the topics of In-app and Side-by-Side extensibility at the SAP TechEd Barcelona.
You find the slides here: https://www.slideshare.net/lechnerc/extensions-in-the-age-of-s4-hana
You find the slides here: https://www.slideshare.net/lechnerc/extensions-in-the-age-of-s4-hana