How to change and edit .scene files via code in CE.SDK, so that we can automatically convert SVG code lines into .scene code and avoid double work?

You can use the CreativeEngine API to create .scene files from scratch or load and edit existing ones.

You can find a quick start guide for the Engine API on the CE.SDK documentation website. Here is the link to the guide here.

Additionally, the Engine API is also available in the Full-Featured CreativeEditorSDK UI package. You can refer to the CreativeEditorSDK quickstart guide to getting started with this UI package and access the Engine API using let engine = editor.engine. Here is the link to the quickstart guide.