Right-click anywhere on the line and select FUNCTIONS - Create offset or use the shortcut O.

A parallel green line is generated in the graphic where you click on the desired side to determine the offset. If you don't use any functions under SNAP or POSITION, the parallel line will inherit the same properties as its parent.

You can also use Create offset with a relative height as a function under SNAP. There are also other options for height and slope. With these options, you can create a slope with a desired inclination.

You can also use Create offset with a fixed length. This function is available under POSITION- Length. There are also other options for perpendicular, position, and cut/fill. With these options, you can create a slope cutting through or filling another object in the scene.