Since Qt5.7, there has been a new version of the QtQuick Controls: https://doc.qt.io/qt-5.11/qtquickcontrols2-differences.html
The version 2 should be faster and take less resources.
We are actually using the version 1.
All QtQuick 1 item don't have an equivalent in QtQuick 2 but we need to find on how to update to QtQuick 2.
Note that we can't commit this as long as we have Qt5.6 as minimal requirement.