For z-stack processing, you may try the following ImageJ-macro with the latest version of the plugin (please update!).
//plugin "Contour_Curvature.class" version 1.0.3 or newer required
//macro version 2021-02-22
requires("1.53h");
Dialog.create("Contour Smoothing");
Dialog.addNumber("Smoothing", 8);
Dialog.addNumber("Contour Points", 400);
Dialog.show();
coef=round(abs(Dialog.getNumber()));
smpl=round(abs(Dialog.getNumber()));
setBatchMode(true);
run("Remove Overlay");
for ( i=0; i<nSlices; i++ ) {
setSlice(i+1);
run("Contour Curvature", "coefficient-pairs=[coef] contour_samples=[smpl] smoothed");
Overlay.activateSelection(0);
roiManager("add");
Overlay.remove;
}
run("From ROI Manager");
setSlice(1);
setBatchMode(false);
exit();
//Paste this macro code to an empty macro window (Plugins >> New >> Macro)