I too would like to put my vote in for this feature.
Our use case is: Our software has many (7+) areas which share common functionality. We have created several sets of test cases to cover areas of common functionality. Each of the test cases has several steps involved. The test cases are arranged in TestRail using sections for major functional areas.
In order to ensure these “common test cases” are covered for each functional area we are forced to either make copies (which then need to be individually maintained, not practical) or make placeholders referencing the common test cases. If we use the placeholder method it is extremely awkward during Test Runs and does not even allow executing the test steps as we might for most test cases.
We need more than a reference link to a test case. We need something that during test run will substitute the entire test case as if it were copied so we can execute against it. The “copy” should be made at execution time to ensure the most recent version of the test case is referenced. And, of course, test run history should appear as if the test case was actually copied there.
Regarding history, defects, etc. these should be recorded in history of the ‘common test case’ somehow referencing the section/subsection in which the test case was executed.