
There is disassociation between selectors and different breakpoints / media-queries. In that, when viewing selectors (for example in ‘All breakpoints’) you are not made aware that there might be matching selectors set in other breakpoints.
I therefore suggest, it would be really helpful, if there were visual indicators just beneath each selector (on whichever current breakpoint you’re currently in) to show that this selector also exists on one or more others.
This marker could either be a colored, circular marker; or a small visual icon (as seen on most other responsive design UI’s, this is most likely to be a mobile, tablet, laptop, desktop icon …but could just as easily be symbolic of small, medium, large, extra-large). This marker would correspond to breakpoints in the dropdown breakpoint selector.
In addition, markers could be made clickable - taking the user to that breakpoint, scrolling until the selector (highlighted) is in view …making it even easier.