Get tab depth via script

Try

function OnInit(initData) {
    initData.name = 'TabDepth';
    initData.default_enable = true;
}

function OnAfterFolderChange(afterFolderChangeData) {
    var currenttab = afterFolderChangeData.tab;
    var td = currenttab.path.components;
    DOpus.Output('Tab Depth = ' + td);
}

See also here.