In an editable QtQuick ComboBox, when pressing Enter, the accepted() signal is emitted. "This signal is emitted when the Return or Enter key is pressed on an editable combo box. If the confirmed string is not currently in the model, the currentIndex will be set to -1 and the currentText will be updated accordingly." - this is a citation from https://doc.qt.io/qt-5/qml-qtquick-controls-combobox.html#accepted-signal. The problem is that editText string property and model strings are compared by case-insensitive instead of case-sensitive way (as it is documented). So if you type "one" and your model contains an item "ONE", the content of editText is changed to "ONE" and then onAccepted() is called. It prevents from adding strings in different cases to the model.