Sometimes our customers want to consume Codecov API data in third party applications. Codecov does not currently have master API key functionality. However, you can use your personal API key to view all org or subgroups, or have an admin create one with a machine user who has access to all repos.
You can create a machine user that has access to all orgs and groups, log into Codecov with that user, and generate an API token. This token would then have access to everything the machine user does in the Codecov API.