Yesterday I fixed my keys’ clip in 9 lines in OpenSCAD:

difference() {
    union() {
        cylinder(d1=8,d2=10,3);
        translate([0,0,3]) cylinder(d=10,6);
        translate([0,0,9]) cylinder(d1=10,d2=8,3);
    }
    translate([0,0,-0.1])
        cylinder(d=5.6,12.3,$fn=36);
}