I am afraid there is no good enough answer for that.
There are tools and methods but they all have major disadvantages that the people you report to should be aware of.
Test coverage, how many tests/checks out of the entire test set were run. The problem here is that you measure the percentage out of the tests you have and not out of what should be tested. ...
Today you can use many Test Management tools to contain the results of your automation. These tools also provide a variety of dashboards and reports that can represent your coverage in any way you like.
Since your tests are E2E the best tool for you is probably PractiTest - this tool has all End-to-End modules, from Requirements to test executions and bugs. ...
Michael Bolton proposes testing coverage as:
“X coverage is how thoroughly we have examined the product with respect to some model of X”.
And he completes:
"Test coverage, like quality, is not something that yields very well to quantitative measurements, except when we’re talking of very narrow and specific conditions."
Being that, you can think ...
The methods and tools of measuring the coverage depend on two things:
Coverage of what your going to measure
If you want to measure the code coverage what is the PL your app is written in
In the case you'd like to measure the coverage of requirements the things are straightforward. Just calculate what part of your requirements are covered by the tests ...