It’s recommended that you develop your functions locally and publish to a function app in Azure : Develop and run Azure Functions locally | Microsoft Learn
Local development environments
Visual Studio Code (Azure Functions extension for VS Code), Comand prompt or terminal (Azure Functions Core Tools), Visual Studio (Azure Functions Tools), Maven (Maven Archetype supports Core Tools for Java functions).
Don't mix local development with portal development in the same function app. When you create and publish functions from a local project, you won't be able to maintain or modify project code in the portal.
Local project files
Triggers & bindings