You can't use the shortcut buttons for this, but you can set the default schedule to whatever you'd like. Just fill in the popup dialog, and click on the 'save these values as default'. In your case, just type "tomorrow at 10:00" as the send time, and every time you open the send later popup it will auto-fill with that value.
It's not quite as slick as using a shortcut button, because you can't execute it with a single keybinding, but you can still do "Ctrl+Shift+Enter" (or Alt+Shift+Enter, depending on your settings), and then hit enter as soon as the popup is displayed.