I have googled this and can’t find an answer as I can’t find the correct keywords (I guess).
If I draw a shape (say a box), and then move it up and then draw another few things before returning to that first box, how can I then move it back down and be assured it is on ground zero, or the base plane or the ground (whatever it is called)?
One way would be to grab the box at a corner with the Move tool and type [0,0,0]. This will put the point you grabbed the box by at the origin. If you only want to move it straight down to the ground plane type [, ,0] (no space required between commas in this second one. The forum software deletes a comma without it.)
(Optional) To move your item a precise distance, you can type either of the following during or immediately after the move:
Distance: The number you type can be positive or negative, such as 20’ or -35mm . If you specify a unit of measurement, that unit overrides your template’s default units. For example, you can type 3’ 6" even if you are using metric system as your default.
Coordinates: The Measurements box accepts global or relative coordinates. To enter global coordinates, use square brackets, such as [3’, 4’, 5’] . To set relative coordinates, use angle brackets, such as <3’, 4’, 5’> .
Another option would be to hide the box. Then when you want to work on it again you could unhide it in the Outliner panel, or select Hidden Geometry from the View menu, then right-click Unhide the box. Or you can use Edit/Unhide/All.