Where do I see a full, exhaustive list of the resources a given Google Cloud Platfrorm project uses?

I have just logged in to a Google Cloud Platform account, and it has several old Projects. I’d like to clean up by deleting the ones I don’t need, but for that I need to see a full list of services each Project uses.

I went to the Cloud Resource Manager, and it mentions a Compute Engine Service Agent here and there, but that’s it. I know one of those Projects must have some API Keys that I still need, but neither this page, nor the Billing page tell me which one.

Searching didn’t help. This looks like the closest, but doesn’t make any sense to me and looks overcomplicated for such a simple task.

Is there one single page that will show me everything a given Project uses, so I am informed enough to decide if I still need it? Please help!