Now I put a copper zone on the top layer and would like to isolate the copper 6mm around the circular holes trying not to affect the other edge cuts.
what would be the most efficient way to do that considering I can create those 6mm offset holes in my CAD software??
In my experience, holes are a little bit quirky in KiCad. Knowing what I know, I would probably:
1)Use your CAD software to draw the holes.
2)Import the new DXF.
3)Save the PCB and edit the holes with a text editor to move the clearance “lines” to the proper layer.
You will probably want to also use the text editor to “lock” all the holes into place. Or, if you don’t, you might find that they vanish if you have to re-import the netlist.
The proper way would be adding through hole pads and define there the 6mm clearance in the pad properties editor. Then center the pads in those Edge.cuts circles you imported.
Another kind of weird workaround is making thicker the arcs/circles that define your mounting holes.
If the line thickness of the arc is 1mm thick, you will have a clearance of 0.5mm to the actual edge. With 12mm thick lines you’d have your 6mm cleareance. This is a hack, an exploit of a questionable behavior of the drc that may change anytime without prior notice.