I cant answer that question with full certainty, because I dont have 3d engrave available in my software right now, but essentially its just a grayscale engrave that theyve already figured out the settings for you.
The glowforge 3d engraved token they posted took 2 passes to get to the wanted depth. Im assuming if you set the power max very high, and the speed very low using manual settings it would achieve the same result. They might be varying power and speed based on which pass it is (and whether or not you have a pro, and what material), so I cant tell you what that might be, but you can tell it to do passes at whatever settings you want.
I think I mentioned this before, but it might be possible to do a lower power fast engrave as the last one in the series to just clear off the surface of charred material. @karaelena sent me a video recently of a wood test from another laser manufacturer and they said they use this technique to clean things up at the end. Ill see if I can find it and post it.