Hi Marco, what is it that you are trying to achieve by doing that?

There would not really be any kind of "improvement" to your object by what you are trying to do, and in fact it would usually result in worse geometry because you would no longer have lines being turned into analytic plane faces when they were extruded, you would instead have a general surface object which would no longer benefit from more simplified calculations like intersections and projections.

Right now as a side effect, if you export your joined curve to STEP format, STEP does not have in it the concept of a segmented curve, so MoI combines the segments into one long spline curve, and when it reads it back it will only break it apart at sharp corners, so that almost does what you want except any line segments in the curve will become degree elevated to the highest degree segment which will make the lines have one or two additional points in them.

In the future I expect to have some curve merging mechanism built into MoI to do what you want, but for a case like you show here where you've got something constructed out of lines and arcs it is better to keep those as separate segments so you get planes and cylinder analytic surfaces when you extrude them.

- Michael