In HTML5 every element can have an attribute 'translate' (https://html.spec.whatwg.org/multipage/dom.html#the-translate-attribute). If this attribute has the value 'no' an element is not to be translated.
Studio's embedded content processor for HTML allows you to define that a specific element with attribute translate="no", but not a general rule for all elements with that attribute.
For example, this rule is is possible for element 'a':
a[@translate="no"]
But you can't define a general XPath rule for all elements. This is not possible:
*[@translate="no"]
Currently, to fully support the translate="no" attribute, you have to add a separate rule for each of the 100+ elements in HTML5.