Joining filleted curves into single curve

There’s probably a simple solution for this but damn if I can figure it out. I want to join several curve segments that have been filleted, into a single curve, which seems to initially work by simply invoking the Join command. However, if I use this “single” segment to trim a surface, then use the edges of this trimmed surface to create the sides of my object, by Lofting a surface to another curve on a different plane, all seems fine. However, when selecting the edges of the surfaces to fillet the surfaces, Rhino wants to only select segments of the edges, that translate into the segments that were from the original curves before I joined them. It seems the “joined” curves I used to trim the first surface maintain their original segments on the surface edges, when trying to fillet. I’m new to the Rhino world, so I expect an answer that could possibly make me look like an idiot, but if it solves my problem, it’s all good. Thanks !!

You’ll probably have to send a file to get a good answer, but, generally, a curve that is joined to others doesn’t become one single curve. It becomes a polycurve existing off several segments.
When you want to fillet the surfaces, you’ll have to select all edges one by one or use the chain option to automatically select multiple edges.