Working with Sketch Curves in 3D

Use Enable 3D Sketch to switch to sketching mode in 3D.

You can use the following sketch tools in 3D mode:

You can use the following tools from the Sketch group to change curves in 3D mode:

Create Rounded Corner Create Rounded Corner can be used on curves when they are coplanar.
Create Corner Create Corner can also be used on coplanar curves.
Trim Away Trim Away can be used to trim curves in 3D mode.
Split Curves Split Curves can be used to split curves in 3D mode.