@redasobeh wrote:
Does that mean there is no way to join them into a single polyline?
Correct, without some repairs there is no way.
1. the green arc is drawn at the wrong Z-value. (image_01)

2. The cyan arc and the blue polyline don't touch each other (Image_02)

3. The objects don't share the same XY-plane
=> So you can never join all 4 objects to a polyline
If you repair the drawing errors I mentioned above you could consider to convert to a 3DPolyline. But this object type (3DPoly) must not include arcs. So you have to substitute the arcs by a bunch of short line segments (as you have done in the blue polyline). Only this way you have a chance to get ONE object (a 3DPoly) for the curve.
Jürgen Palme
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