Contextual Kerning for triplets L'A and A'A

I purchased Glyphs this February and I have been working on a multilayer/chromatic display font. I am really happy with the software and my font is nearly finished now.

I have a problem with the contextual kerning “kern feature/kerning on top”. I read the tutorial and everything seems pretty clear:

I have written the following instruction but I does not change the triplet kern. This is the original position of the triplet:

and this is after applying the code:

I have complied the code and activated “kern” on the text editor window.

I have entered a few different values and also created the triple A’A but nothing has changed either. Is there anything else I need to activate that I am not doing?

Thanks for your help in advanced.

The custom kerning feature is not previewed in the edit view. Please see how it looks in TextPreview or Indesign.

Correct! I have just tested the values in InDesign and it works perfectly. Thank you very much for your help.