I pushed new commits to the PR that changed the Korean, Japanese, and Indian samples and the help message.

Korea: The line is now the first 10 chars of Dong-hee Na's suggestion.  Thank you for helping (and Louie for the cc).

Japan: The line is now the hiragana and katakana versions of the 5 vowels.  As far as I know, 'kanji' are a subset of CJK 'hanzi', with different pronunciations and possibly different meanings, so I see no need for any here.

India: The second line is now Tamil digits and vowels.

China: I found the chars, with translation, including the one simplified/traditional pair, on Wikipedia.  I did not know if more pairs would be a good idea or not, and I do not know of others.  Louie, if you have a better idea, please post it (with translation ;-).

Dialog size: The height is about 710 pixels, 10% larger than before the additions to the General page a month ago.  So it was previously too tall for 800 x 600 and still fits 1024 x 768.  Further expansion should mostly be in width, but there is some vertical room.

Spaces and labels: I initially had neither.  I could hardly stand to look.  The label are needed for people who do not recognize the character sets, and I use them to make three general points in the help entry: tk uses whatever font it can to cover most of the BMP; fixed font sizes for Latin font only apply to Latin chars; and right-to-left is handled correctly.

Latin1: I consider the Windows fontchooser to be an anti-model for this issue in that it is limited to alphabetic characters and confuses 'language' with 'character set'.  Western, Central European, Baltic, Turkish, and Vietnamese languages all use latin characters.  The non-ascii, decorated versions are 'covered' by the non-ascii Latin1 line.  Á is already present. Â is intended to represent all circumflexed characters, including Ô. I intended the repeated use of A as base character to imply that.  I not sure if using a different base for each decoration would be better.  Similarly, Ç covers Ş.  I am thinking about using fewer symbols and more alphabetic characters.  It might be a good idea to add something, such as Ğ, from the Extended block, beyond \u00ff.

User additions: This would be a separate issue, see #31777.