The event-based rule for "Element in viewport" is an awesome feature. The problem is that it only runs once per HTML page view. As sites migrate to SPA the need for a setting to capture each time an element appears in the viewport is becoming more necessary. Perhaps an option to set a maximum number of times the rule can fire per HTML page view, between 1 and infinite. An option to limit the rule from firing more than once per unique HTML element would also be a slick addition. As in, if you have 3 internal campaign promotions on a page that all use the same CSS Selector, the rule would fire three times on the page as each unique element appears on page. But no "repeats" of the same unique element.
