Hi Axel, once you have installed it into MoI's commands folder (either inside the MoI installation folder, or for v4 use the one in appdata/Moi/commands) that will make a new command called BatchFilletCurves available. You can set up a shortcut key with BatchFilletCurves as the command name, or type Tab and type in BatchFilletCurves and push Enter to run it.

To use the command, select all the curves you want to fillet, then run the command. At the prompt for "Pick fillet radius", type in your desired radius and push the 'Done' button and the fillet should be applied to all corners of all the curves you selected.

If you're still having problems can you please post a .3dm file with the curves in it?

- Michael