I’m not sure I fully understand. When you view a test case, you can see it’s execution history. It would appear that the execution history is for the current definition of the test case.
Testrail already has the history and “tests & results” tabs. It would be ideal if there was a way to designate that change has occurred. On the tests & results tab, there could be a line inserted that says “— test case changed --” which would alert you to when changes have occurred over the execution time line.
We recently had a developer digging and digging because a test case was failing for him when the execution history was all green only to realize hours later that the test case had been recently updated.