I was incredibly excited to see that Affinity Designer had a "sculpt" feature for lines as the line sculpting workflow is something I love in Blender's Grease Pencil Tool and have wanted something similar in a regular vector program. For reference, in my experience line "sculpting" refers to the ability to toggle between a set of subtools to reshape a line and perform other operations such as changing line width on the fly using a tool that feels more like a brush than a cursor selecting individual nodes.
I was saddened to discover that the Affinity Designer "sculpt" feature appears to have nothing to do with actually "sculpting" a line. It simply enables one to extend an existing curve object.
There's nothing wrong with the feature itself. It's just that the name is incredibly non-descriptive for its actual function. Calling it something like "Extend" would be much more clear.
I will continue to hope that someday a true line sculpting tool will be added to AD (maybe there is one and I just haven't found it yet).