This years robot is a milestone for us in terms of the amount of 3D printing that has gone into it.
It started last year with the discovery that you could design really complicated things (that worked!) when we made custom mecanum wheels.
Onshape is a web based parametric CAD package. It seems that the hobbyist community mostly uses Fusion 360, but for us that was a non-starter because it is Windows only, and I no longer have *any* Windows machines.
Onshape works completely in your web browser and stores its data in the cloud, so I can drop into it for a quick design session from work or at home without having to install anything. And with their android app, also while commuting on the train.
They have a plugin system too for people to write custom tools when the existing ones are insufficient. This year we used Nut Pocket (which generates pockets for nuts, so that you can use standard fasteners in your 3D prints) and Bevel Gear Generator (which generated our main drive gears).