In the 16.1.1 release, the Originating Idea field is now hyperlinked to the idea that was used to create that project. Is this a value you can access to capture the Idea ID or via API?
Release : 16.1.1
If you use the REST API, you can fetch the attributes for the project. There are two fields for the originating idea.
"originIdea": "my new idea",
"originIdeaId": 5277185,
The web browser will also show the idea id value in the link for the originating idea from the project
https://servername/pm/#/idea/5277185/details