I haven’t been able to find clear documentation on this topic.
Also, do all functions within a Function App need to be in the same function_app.py file, or can they be separated into different files? If separation is possible, how should the project structure look?
Any insights or references to documentation would be greatly appreciated!
Yes. In fact, in general you need a "normal" Function (e.g. HTTP trigger) to start the Durable Functions orchestrator.
I haven't made Functions with Python, but it looks like you can split to multiple files: https://learn.microsoft.com/en-us/azure/azure-functions/functions-reference-python?tabs=get-started%2Casgi%2Capplication-level&pivots=python-mode-decorators#folder-structure.
additional_functions.py: (Optional) Any other Python files that contain functions (usually for logical grouping) that are referenced in function_app.py through blueprints.
It explains the concept of blueprints further here: https://learn.microsoft.com/en-us/azure/azure-functions/functions-reference-python?tabs=get-started%2Casgi%2Capplication-level&pivots=python-mode-decorators#blueprints