... В частности, необходимо сделать так, чтобы во время программного изменения списка QComboBox'а (включая текущий индекс), тот (QComboBox) не генерировал сигнал currentIndexChanged(). ...
Пользуйте сигнал activated()
There are two signals emitted if the current item of a combobox changes, currentIndexChanged() and activated(). currentIndexChanged() is always emitted regardless if the change was done programmatically or by user interaction, while activated() is only emitted when the change is caused by user interaction.