Is it possible to create a blurred Matte in Harmony advanced?

I need to apply a matte to a blurred layer but i don’t want the matte to be sharp-edged, In order to apply the blur effect to the matte layer i need to create a group but when I try to drop the matte-art layer in the cutter a window shows up saying it cannot link a layer from another group.
Can anyone help me out ? is there a way to make a blurred mask in harmony adavnce?
Thank you very much!