Extensions are the way to customize Dynamics 365 for Finance and Operations. Microsoft is committed and working on scenarios where customers, partners, and ISV solutions will need extension capabilities. All platform and application updates are delivering new extension capabilities, as requested by customers. 

Extensions provide the following capabilities:

• Creating new model elements.
• Extending existing model elements:
  • Adding a new enum value to existing enums
  • Modifying an existing extended data type
  • Modifying existing fields or adding a new field to existing tables
  • Adding an index to existing tables
  • Adding relations to existing tables
  • Modifying properties of existing tables
  • Adding methods to existing tables
  • Adding a new data source to the form
  • Adding form captions and changing control properties
  • Extending electronic reports
  • Extending reports by creating a copy of existing reports
• Customizing business logic. Ways to customize business logic include the following:
  • Creating event handlers to respond to framework events, such as data events
  • Creating event handlers to respond to event delegates that are defined by the application
  • Creating new plugins
  • Using method wrapping and chains of commands