The keyboard shortcuts on Windows for accented characters need to be entered as follows: hold down the Alt key, then enter the decimal number for the character (preceded by a zero) on the numeric keypad.
Example:
the character à is U+00E0; E0 is decimal 224, so what you have to type is Alt+0224.
Unfortunately so far I have not succeeded to enter any characters greater than U+00FF (255). This "should" work; I will do some further research. But for right now I have to go out.