Hi Anna

You can display each button on the ribbon as the 'small' icon, rather than large, which will 'stack' the icons into the group. For example:

You don't get to control how many are stacked though, by default the ribbon is 3 'small buttons' high.

To set the icons to 'small', when you are customising the ribbon, select the ribbon item to be displayed smaller, then click Properties. On the Command Properties dialog, unselect the "Always display large image" option, then click OK. Do this for each button that you'd like to display in the small format. Once completed, click OK on the Customise Ribbon dialog and your ribbon will have your new settings.

I hope this helps get you to be close to what you're looking for.

Kind regards

Thank you Helen.  It worked.  Thanks again

Awesome, glad it worked out for you! Have a great day and weekend