miro's answer is brilliant, i'm just going to write it slightly differently
There are a four composite font files.
The four are
C:\Windows\Fonts>dir *composite* /s/b
Looking at them once sees that, for example,
GlobalMonospace.CompositeFont has 0590-06FF and the fallback fonts listed, just one, is Courier New, which has Aleph. But Miro determined that that's not the composite file used, and that the one used is
Open this file
\u05D0 so you have to scroll the file down to get to where i'm showing in the pic, but that's the section to look at
The composite font file lists a family of fonts to act as fallback fonts for various ranges of unicode characters, including
0590-06FF (which is the range that includes 05D0/aleph)
Unicode = "0000-052F, 0590-06FF, 0750-077F, 1D00-1FFF, 2C60-2C7F, FB00-FB0F, FB1D-FBFF"
Target = "Segoe UI, Tahoma, Arial, Arial Unicode MS, Microsoft Sans Serif, Lucida Sans Unicode"
Scale = "1.0"/>
Charmap can reach as far as FFFF which is far enough. Charmap show that it's not in segoeUI. But it is in Tahoma.
Babelmap is interesting because it can show characters past FFFF (not necessary in this case), and also it can show what fonts on your system have a particular unicode character. But to see what font is actually used in practice by notepad, as a fallback font, you need to check that GlobalUserInterface.CompositeFont file. Then look in charmap or babelmap for the first font with the glyph/unicode character that you want.
Babelmap has composite fonts but I think they are custom ones not specifically the custom one used by windows. But one could usefully use babelmap to search for which font has a unicode character, or to look at what characters are within a font, even beyond FFFF.