Adding a dynamic/Incrementing variable in Gherkin Scenario in Test Log

You'd have to use the 'Scenario Outline' keyword instead of 'Scenario' to accomplish what you're asking. Combined with the 'Background' keyword or Before hook that will run some logic before every scenario this could potentially allow you to create dynamically named titles, BUT it seems overly complicated IMO (see here).

I think the simplest solution is to just write to the log directly. Here's and example function:

function logDynamicTestName() {
  var i;
  for (i = 0; i < 4; i++) {
    var Name = i + " Test Case";
    Log.Message(Name);
  }
}

Not sure what your intent is by doing this or how you are running your tests so I am making some assumptions, but if you're only wanting to track dynamic names/titles in the log I would use the logging function above - IE: make the 'Background' step definition write to the log and increase your counter by 1.

Example in BDD:

Background: Write test case name to the log

Scenario: Test Case
  Given/When/Then

 and your step definition would look something like:

When("Write test case name to the log", function (){
  # set a default value of 0 or 1 to the project counter variable then...
  var Name = Project.Variables.Counter + " Test Case";
  Log.Message(Name);
  Project.Variables.Counter++; 
});

Additional references below: 

[Gherkin - Background] 

[Gherkin - Before]