As you know, built-in functions Cinema 4D does not allow to connect a segments of a single spline. But now you can do it with this a little but very useful plug-in! Pretty fast, pretty easy!
Start with any un-joined splines.
Select two points and use the “Get” button to automatically set the correct distance tolerance. Parameter can be adjusted with minimum and maximum value to find points more accurate. Increase value little bit, if current tolerance is not enough.
The Join mode creates a new segment between connected points.
The Weld mode weld two spline points into a single point.
The newly welded point will lie at the mid-point of the welded points.
Customize interpolation, chamfer and segment length options for connected points.