Certainly "Group to Layer" would be handled by the
selection" option in the "New Layer" dialog.
Not sure about how much or if at all "Layer to Group" would be needed.
Can you provide a use case?
Just convenience - when you work inside some group it's convenient to
have it as layer, so as not to have to "enter" it all the time. When
you're done working inside it and want to position or transform it,
you need it to be a group again.
In old files, people may have used groups instead of unavailable
layers as a way to organize stuff. It would be nice to allow them to
convert these to proper layers easily. Making a layer with selected
group and then ungrouping it is not too elegant, and as we now know
ungrouping may not preserve appearance for textpaths.
Also there's a slight didactic value in these commands: they emphasize
the relation between groups and layers which is an important thing to