showing a lot of widgets in qt5 is slow - c++

Question

I'm developing an program that allows you to communicate with an Engine control unit of a small turbine. The ECU is configured using 255 8-bit numbers stored in an EEPROM (ECU communicates over RS232). each number represents one of the engine's settings.
So to make sense of this we have a file that describes the meaning of all these settings and this is loaded into my program, which generates a row of 15 standard QWidgets per setting.
I also implemented a way to categorize these settings, for example, all fuel consumption related settings belong to one category. there's a Qcombobox in which you can select which category you want to filter. clicking it calls the following function:
void MainWindow::on_listCategories_currentTextChanged(const QString &currentcategory) { //filter categories
//ui->checkBoxShowDifferences->setCheckState(Qt::Unchecked); //ugly hack!!
setUpdatesEnabled(false);
if(currentcategory == "ALL") {
for(int i=0; i<RegistrySettings.size(); i++) {
if(RegistrySettings[i].Policy < static_cast<int>(TMC_Program.CurrentActiveAccessPolicy)) {
hideOptionWidgets(RegistrySettings[i].address);
continue;
}
if(ui->checkBoxShowDifferences->isChecked()) {
if(RegistrySettings[i].value == RegistrySettings[i].compareValue) {
hideOptionWidgets(RegistrySettings[i].address);
continue;
}
}
showOptionWidgets(RegistrySettings[i].address);
}
} else {
for(int i=0; i<RegistrySettings.size(); i++) {
if(RegistrySettings[i].Policy < static_cast<int>(TMC_Program.CurrentActiveAccessPolicy)) {
hideOptionWidgets(RegistrySettings[i].address);
continue;
}
if(RegistrySettings[i].category != currentcategory) {
hideOptionWidgets(RegistrySettings[i].address);
continue;
}
if(ui->checkBoxShowDifferences->isChecked()) {
if(RegistrySettings[i].value == RegistrySettings[i].compareValue) {
hideOptionWidgets(RegistrySettings[i].address);
continue;
}
showOptionWidgets(RegistrySettings[i].address);
} else {
hideOptionWidgets(RegistrySettings[i].address);
}
}
}
setUpdatesEnabled(true);
while hiding works perfectly fine, when selecting "ALL" it needs to show all the hidden widgets, this is incredibly slow! it takes around 5 seconds to display all the widgets!
The code responsible for showing all the widgets is this:
void MainWindow::showOptionWidgets(int addr) {
if(addr < 0 || addr > 255) {return;}
QStringList WidgetNames = generateOptionRowWidgetNames(addr);
for(int i=1; i<WidgetNames.size(); i++) { //number 0 is a qhboxlayout and not a qwidget so it won't find it
QWidget* widgetToShow = ui->scrollAreaOptions->findChild<QWidget*>(WidgetNames[i]);
if(widgetToShow && widgetToShow->isHidden()) {
widgetToShow->show(); //extremely slow!
}
}
}
is there a way to optimize this?
note: all widgets are standard ones! just labels, checkboxes and buttons, generate optionRowWidgetNames only generates a simple QStringlist with fixed strings that only have the corrosponding settings number attached to them.