How do one change the font size for the item text on the left bar menu?

I can't figure out how to change the font size for the item text on the left bar menu. I've tried main menu properties custom CSS, font size on the cell, font size on the field etc... Then only place it seems to change it is in the menu editor CSS Style for each menu item which would take a while. There has to be a better way that I am not finding. Any inspiration or direction would be greatly appreciated

Thanks in advance