The Indico.UN project has a unique challenge - to serve not only the United Nations Office Geneva, but also other UN duty stations worldwide. This requires a deep and heavy customization of Indico, as it needs to harmonize complex workflows across multiple organizations. In this session, the Indico.UN team will showcase their technical approach to addressing this challenge. They will present their use of built-in and in-house developed utilities to add UN-specific functionality and customizations to Indico. Additionally, the team will demonstrate how they have reliably extended Indico classes, altered the database schema, injected form fields, intercepted function calls or overhauled the entire permission system, among other techniques. They will also discuss how their development lifecycle interacts with upstream contributions. The aim of the presentation is to inspire attendees with ideas about how they can solve their own complex requirements when developing Indico plugins.