I have the NameMapping open and I am using XPath/CSS selectors. On the right side, there are the different possible selectors. I click on a selector to include or exclude it from the matching. The Highlight button then becomes disabled. I then have to click over on the object tree, to get the highlight button to become enabled. Additionally, when clicking on the object tree, if I click on the same node, it goes into edit mode for the name. So, I have to then hit esc to get out of edit mode, then hit the highlight button. The alternative, is to select a different object, then reselect the desired object and then press the highlight button.
It would be much less tedious and more optimial if the highlight button remained enabled. Make it less mouse clicks to highlight an object after enabling/disabling the selectors.