There is not a formal "dimension tool" in the 3DCW PT. But there are several resources that you can use
1 - you can use lines or shapes to measure distances => select the element => resize object will provide the distance. You can delete it after.
2 - If you are creating several objects => use edit => Duplicate => Duplicate Properties to duplicate and set the distance between the objects.
3 - You can use Edit => Move => to set the exact distance when you move an object.
4 - You can set and use the grid .
Hope this helps.