You should make a module that overides the file here  found in my EE v11:
addons/web/static/src/js/views/form/form_renderer.js

Just for testing purpose you can edit the file and change the number of Smart Buttons you want, here i changed 7 to 10 buttons displayed:

 // Get the unfolded buttons according to window size
        var nb_buttons = [2, 4, 6, 10][config.device.size_class];
        var unfolded_buttons = visible_buttons.slice(0, nb_buttons).concat(invisible_buttons);