There is a tag trigger on the right side of each line. Some of those tags may contain messages. Initially only an indicator icon is shown and the message is hidden. (I draw the overflow for demonstration, but there may be other methods) When the shown icon is hovered, the whole tag would move to the left and showing the message with a button.
Now here is the problem. Firstly I cannot animate the tag with scalable message length in pure CSS. Secondly since I'm using fixed height for each line, I cannot set the right property for vertical alignment for the message text.
Here is my attempt http://codepen.io/rix/pen/DaGyk.