Simply start by making a duplicate of the layer-mask layer. Resulting in two of the same layers.
Now we want to put the two layers into a group. To group the two layers, select one of the layers created, then hold the “shift” key and click on the other duplicated layer. Both layers should then be highlighted.
Next right click on the two layers selected and select “Merge Group” (hold command G). The group should now be merged, thus creating one single layer. This layer can now be edited as a regular single layer. You may choose to duplicate this layer as for you may not want to replete the process should it become necessary.
Hope this helps. Thanks