Loosen (Object->Splines/Lines->Loosen) lengthens the control handles.
Tense (Object->Splines/Lines->Tense) shortens the control handles.
To combine two splines into one spline:
If you want the splines to remain as they are, choose Object->Splines/Lines->Combine Paths. This makes them into one path, but does not move them.
If you want the start of object #2 to connect to the end of object #1, choose Object->Splines/Lines->Connect Paths.
Object #1 is either the topmost object (if all objects are selected at once) or the first object selected (if the objects are selected one at a time, using the Shift key).
Note: You can tell which end of the path is the start by its different color. You can change which end is the start by choosing Object->Splines/Lines->Reverse Path.
