This is how layout sets up a group (layout_maps)

    groups['UI'] = display.newGroup()
    groups['layout0']:insert(groups['UI'])

    -- new button
    elements.btnQuests = loqbutton.newButton {
        spriteGroup = _spriteFactory:newSpriteGroup('BtnQuests_up'),
        up = 'BtnQuests_up',
        down = 'BtnQuests_down',
    }
    group = elements.btnQuests
    groups['btnQuests'] = group
    group.elementName = 'btnQuests'
    group.libraryName = "Btn_Quest"
    groups['UI']:insert(group)
    group.x = 160
    group.y = 412