Menu item list truncated -- Combobox/Popdown -- when hitting screen limits

I found the menu item list been truncated when using a combobox/popdown and the menu box is hitting the screen limits. And found no way to access or scroll up/down not shown items. Gtk3 was allowing to scroll.
Is there a option to allow / enable scrolling for a longer selection list?

Just have a list long enough or the combo box near the bottom of the screen so little room is available to pop down to.