My head is now in the books to get my mind back into the sky before my body goes into the simulator.
Did you remember that if you're more than 200 miles from the airport, and ATC descends you to a lower altitude, you'll lose your descent path indicator... ie., the Chinese glideslope?
When you descend to a lower altitude prior to 200 miles, the airplane re-cruises you at that lower altitude. Operationally this means that you are still in the cruise phase, and the decent path indicator disappears.
While there are other means to in assist descent planning, if you want this tool back in your tool kit now, all you need to do is go the performance page and put in an altitude above the altitude you're cruised at. This puts you back into the descent phase.
Another note on descending...
You're at FL340, and you're supposed to be at intersection HAPPY at 10,000 at 250 KTS, but ATC descends you to FL300. Remember the path has drawn a straight line from FL340 to HAPPY. You've just been cleared down to 300. To get the descent path indicator to provide good information you'll need to take the HAPPY constraints out. Then, when level at 300 put them back in. Your straight line, your path, will be recalculated from your present altitude to HAPPY's constraints.
Enjoy the Journey!