Auto - adjust size of icons in QToolBar after hiding a QAction button

Question

in my GUI program I have a QToolBar at the bottom of my mainwindow which contains a number of QAction buttons for opening various dialogs.

Now, I have adjusted the size (i.e. width) of icons of the QToolBar through the QTCreator interface size policy. The size of icons are set manually in such a way that they occupy the entire width of the QToolBar.

Now, due to some required functionality of my program, I need to disable / hide one QAction button (i.e. the Icon). But when I hide that;

if(myconditions = true)   //when my conditions to hide the button are met
{
    ui->myaction->setVisible(false)
}

The rest of the QAction icons shift accordingly and a blank space (with the width same to the hidden icon) is left in the toolbar.

Can I adjust the size (i.e. width) of icons of the QToolBar through coding so that they occupy the entire space even if one or some gets hidden ? I couldnt find such options in the QTCreator GUI - icon size options.

From the documentation it seems it can be solved using iconSize but I dont know how to use it in code.