Double clicking a Test Case Editor root node helps in navigating to a Test Suite or Test Case referencing the edited Test Case:
If there is a single Editor open which references the Test Case, that Editor is activated.
If there are more than one such Editors open, then a dialog pops where you can choose which one to activate.
If there are no Editors referencing the Test Case, then the list of Test Suites and Test Cases referencing the given Test Case is shown, and you can choose one to open its Editor.