Good points made by FlightDetent.
Having read the original post again, I think that maybe the VNAV mode was a cruise descent? The title of the active VNAV page will tell you. It could be that your sim does not reflect all the functionalities of the aircraft?
Anyway, if VNAV doesn’t do what you want, you can always try VS or FLCH but keep an eye on the FMAs! You may need speed brake to stay on profile without accelerating too much. On the other hand, you (or the auto throttle) may need to add thrust. It takes knowledge of the system and lots of practice to predict confidently which modes will produce which results, given a requirement to reach a level by a waypoint.
One neat feature that your sim may have is on the VNAV descent page. Around the 4R Line Select Key you may see a Waypoint/Altitude line. Normally, this will display the next waypoint in the flight plan that has an altitude constraint associated with it. Below that, you will see some fields labelled FPA,
VB and VS. The FPA shows your current Flight Path Angle, in degrees below the horizon. The
VB shows the current Vertical Bearing between you and the waypoint/altitude (in a straight line, not via the flight plan waypoints). The VS shows you what Vertical Speed you need to achieve the
VB at you current ground speed.
What is really useful is that you can enter any waypoint that is in the Nav Database, even if it is not in your flight plan. You can also enter any altitude against it (provided that it is lower than your current altitude) and the
VB and VS fields will display what you need to do. Then you can either use VS mode to match the required VS and/or you can use any mode and see if your FPA matches the required
VB.
Once you’ve finished with that waypoint, you can delete it and the next flightplan waypoint with an altitude constraint will once again be displayed.
Give it a try!