Introduction:

In the above menu, you can see that the item "Info" and its parent item "Tree Menu" are highlighted by using icon and font.

That is because, through the analysis of the menu, the link URL of menu item "Overview" is the same with "index.htm" you are visiting; and "DHTML Menu" is highlighted for clicking the option "Auto show highlighted popup menu".

Steps:

Click Global > Highlight in Tasks panel and check "Auto highlight current item" option.
You can also check any style settings of Mouse over for highlight items in Styles area and check other options as you like in Options area.