MainWindow.qss

*
{
    background-color: rgb(17, 9, 15);
    font: 35px "Segoe UI";
}

QTabWidget::pane
{
    border: none;
}

QTabBar
{
    background-color: rgb(17, 9, 15);
    color: rgb(166, 164, 166);
    font: 60px "Segoe UI";
}
QTabBar::tab
{
    border: none;
    padding: 12px 0 0 25px;
    font: 48px "Segoe UI";
}
QTabBar::tab:selected
{
    color: rgb(240, 241, 240);
    padding: 0px 0 0 25px;
    font: 60px "Segoe UI";
}

/***/
QTreeView, QTableView
{
    border: none;
    outline: none;
    color: rgb(80, 80, 80);
    selection-background-color: #fff;
}
QTableView
{
    margin-left: 20px;
}
QTreeView::item, QTableView::item
{
    padding-right: 20px;
}
QTreeView::item:selected, QTableView::item:selected
{
    background-color: rgb(17, 9, 15);
    color: rgb(240, 240, 240);
}
QTreeView::indicator:checked, QTableView::indicator:checked
{
    image: none;
    color: rgb(120, 120, 120);
}
QTreeView::item:checked, QTableView::item:checked
{
    color: rgb(120, 120, 120);
}

QTreeView::branch {
    background: palette(base);
}
QTreeView::branch:has-siblings:!adjoins-item {
    background-color: rgb(17, 9, 15);
}
QTreeView::branch:has-siblings:adjoins-item {
    background-color: rgb(17, 9, 15);
}
QTreeView::branch:!has-children:!has-siblings:adjoins-item {
    background-color: rgb(17, 9, 15);
}
QTreeView::branch:closed:has-children:has-siblings {
    background-color: rgb(17, 9, 15);
}
QTreeView::branch:has-children:!has-siblings:closed {
    background-color: rgb(17, 9, 15);
}
QTreeView::branch:open:has-children:has-siblings {
    background-color: rgb(17, 9, 15);
}
QTreeView::branch:open:has-children:!has-siblings {
    background-color: rgb(17, 9, 15);
}

QStatusBar {
    background-color: rgb(17, 9, 15);
}
QStatusBar QLabel {
    background-color: rgb(0, 138, 0);
    color: rgb(240, 240, 240);
    font: 35px "Segoe UI";
    padding-top: -5px;
}