Almost ... I want to select a surface of a volume
object and then convert the selection into
only the edges of this specific surface.
ctrl-a will select all edges of all surfaces of
the entire volume ...

Hi s7r83dg3, to do one surface out of a volume, select that surface with the "drill-in" selection (you may need to zoom in a bit so you can do the second click on an area on the surface that is not nearby an edge), then use the Edit > Separate command to break that surface away from the main object, then do the steps that I wrote previously on the new separated part.

Also after you do the Ctrl+C to copy the edge curves to the clipboard, you can use Undo to undo the separation part, then use Ctrl+V after you are back to the original object after the undo.


Also if you don't have too many edges you can just select whatever edges you want to copy individually or with a window selection instead of Ctrl+A.

- Michael

Also another edge selecting method that may be helpful for your case is the new loop selection option that was added in the last beta: