[quote="Zodler"]Why the Drop-down button that contains "New Folder" is always on when nothing is selected? When you Customize the option
"Always Enable Drop-down" is not selected. So why is it still enabled? (I know the logic, you want to create a new folder!, I want to understand the customization)[/quote]
New Folder is always available, whether or not anything is selected (since the selection is irrelevant to creating a new folder), so the main New Folder button is always enabled.
The button-menu's menu part is also always enabled, since the menu part (by default) is enabled/disabled the same as the button part.
The 'Always Enable Drop-Down' option prevents the menu part from being disabled if the button part is disabled. Since it never isn't disabled, it won't do much.
(Actually, if you go to a folder where you can't create a new folder, like My Computer, then the New Folder button will be disabled, and there the 'Always Enable Drop-Down' option will make a difference.)
The Get Sizes command is already in the Edit menu, and Ctrl-L hotkey, FWIW.
You just need, while in Customize mode, to right-click the Properties button and turn on 'Always Enable Drop-Down'.
There is no default command. There's just a button part, which runs whatever you put in there, and a menu part, which has whatever you put in there. You might be confused by the default toolbar reproducing the button part as the first item in the menus, but it's just a copy of the same command and doesn't have to be there.
The default toolbar is like that to make the keyboard shortcuts more visible.