When combining shapes, you run into a situation where one side of the node is a sharp straight line with no handle and the other smooth with a handle. To smooth out the hard edge, you may need handles on both sides.

If you Convert the node using the context toolbar options, “Smooth” or “Smart”, it affects the existing handle. To add a second handle without affecting the existing handle, all you need to do is:

• Select the Node Tool.
• Mouse over the line and left-click.
• drag/pull the line while clicking.

Now you will have handles on both sides without affecting the existing handle.

After finding out how to do this, it seems obvious. I am sure you will feel the same way too.