If the second word is the literal add, and the remaining tokens are valid layer names, layers are created (or extracted from the removed list) and added to the end of the layer table.
The second form removes the listed layers from the layer table. These can be reinserted from the Layer Editor in the Attributes Menu. Removed layers can also be added to the end of the layer listing by typing ``!layer name'' or with the ``!ltab add'' form of this command.
The third form renames the layer named oldname to newname.