Click a group handle, then choose Edit Group
Attributes from the Staff menu. (Or, double-click a group handle.)
Or, choose Edit Group Attributes from the Staff menu without selecting
a group. The Group Attributes dialog box appears. To display the attributes
of another group, click the spin controls to select another Group ID number.
To use an alternate barline style instead of
the barline style originally defined in the Measure Attributes dialog
box, select Use Alternate Group Barline, then select the barline style
from the palette for the group.