Is there a way to configure one of the HTML file types in Trados Studio to inherit the Not Translatable status from a parent node?  I can't seem to get it to do this; the Translate condition for attributes seems to function independently from the parent.

For example, I have the following HTML:

<p>This is a sample image: <img src="some_image.png" alt="Sample image" /></p>

If I modify the parser rules to make the P element Not Translatable, the alt attribute of the img element is still translatable in the editor.  The actual paragraph text ("This is a sample image:") is not translatable.  When I look at the IMG parser rule, I see that the alt attribute is set to Translate=True.  There doesn't seem to be a Translatable (but not in protected content) option for attributes, which is what I would want in this case.

Is there something I can configure differently to get the behavior I'm looking for?  I'm using Trados Studio 2015; both the HTML 4 and HTML 5 File Types produce the same results. 

My real-world use case for this functionality is to add a custom parser rule to the HTML File Type and then use that tag to indicate content that should not be translated in HTML files.  I suppose I may be able to comment out the content I don't want to translate...  I'll need to test that approach to see if it works as expected.