The font section says:

 

To see a complete list of fonts, execute the following in the *scratch* buffer by pressing C-x C-e at the end of the line:

    (insert (prin1-to-string (x-list-fonts "*")))

https://www.gnu.org/software/emacs/manual/html_node/efaq-w32/Font-names.html#Font-names

I have 3375 fonts installed and the above  expression created a very long line which 

was too much for my Emacs 26.2 and I had to wait some time until it became 

responsive again.

I suggest replacing the expression with this, which does not create a long line

and clearer too:

  (dolist (font (x-list-fonts "*"))

    (insert font "\n"))