Styling admin page rows in order of importance (checkboxes)

The problem you are seeing is that you have your declarations of the same importance from a CSS standpoint.

If you add another style to give it more preference:

#cqrm-current-item-list tr.cue-deletion.cue-coming-soon, #cqrm-current-item-list tr.cue-deletion.tr.cue-coming-soon *{

background-color: #fbb !important;
filter: alpha(opacity=100) !important;
}

Or move the cue-deletion below the cue-comingsoon declaration you should find things work as wanted.

In CSS, # (id) has an order of about 100, . (class) has an order of about 10, and a tag has an order of about 1…

And later declarations with the same or higher weight override those that are earlier.

Looking at your two declarations, they both have

#(id) tr(tag).(class)

This means they have equal weight of about 100 + 1 + 10

Making one more specific (as shown above) will give it an extra 10 weight and override the other. Making the more important later than the less should have the same effect as it will override the other.