"Well, there has been a bit of a paradigm shift in the way C5 models compared to C4 and it looks like you don't like it. "

Aware of that.  Not sure why they found it necessary to prevent certain operations, especially as the prevention is inconsistent; sometimes it works, sometimes it doesn't.

"Basically you can't connect 2 polylines using the "Connect" or "G" hotkey anymore, you will get that "cannot add edge in the middle of polyline mesh" error which is the one I think you meant in your post.  What you can try to do is Dynamically extrude each of the polylines in the same plane and then connect the 2 polymeshes  with the "G" hotkey to form your new mesh. You can connect two polymeshes with the connect tool just fine."

Sounds like an interesting work-around and thanks.  I have had numerous problems connecting different meshes, however.  Carrara hates to add a line between meshes and will generally not do it.  It will rarely loft (but sometimes does it perfectly)...and if you weld, you get some very odd broken shapes as Carrara re-arranges one or both meshes to suit it's peculiar ideas of order.

And it rather begs the question: if this is an excellent modeler, why do common tasks require huge work-arounds?  I can understand (though not agree with) wanting to push a particular style of modeling.  The problem is that every complex mesh and every iterative build WILL arrive at a situation where a non-standard join is the best way to fix a problem.  Carrara has apparently decided that no mesh ever has a problem.  That their own loft and boolean tools are error free, that their line tools respect mesh flow -- and all of this is far from the truth.

To add insult to injury, they haven't given any indication in the software about what they see as the correct method.  Why the huge work-around for a simple pedal shape with a raised decorative ridge?  What method was in their tiny brains that I was supposed to follow to make this five-minute shape?  If they would just tell me, I'd leave the work-arounds -- and the crashes -- and use that method instead.

Mac, by the way.

(Which is one of the reasons I haven't dumped Carrara and moved to Hexagon.   I still wake up in the middle of the night screaming from Hexagon 1.1 and 2.0 on a Mac!)