Label_anchor is a new setting that controls onto which atoms residue labels will go. Selecting L > Label > Residues creates labels for your object or selection and they default to the alpha carbon. You can set Label_anchor to 'CB' or any other atom type to label on that atom instead of the alpha carbon.
Note: If you set this to an atom that doesn't exist in a residue, that label will be blank. Eg, setting this to "CB" will not label glycine residues.
# default labels will be on beta carbons now set label_anchor, "CB"