With the assistance of Rob from Fontstruct.com, I figured it out.
The English good assortment will depend on having a sure set of characters.
There are numerous “official” requirements that inform folks what characters should be included in a font for what sort of language help, e.g. https://en.wikipedia.org/wiki/ISO/IEC_8859-1, however there is no single normal that completely each font foundry and font-vending web site makes use of. I learn a criticism that two foundries producing two fonts with the identical set of glyphs can declare wildly completely different language help.
However there did not appear to be a straightforward manner (like a spreadsheet) of discovering out the minimal variety of characters wanted for English help.
There are web sites like FontDrop! https://fontdrop.information/ and instruments constructed into font-designing software program into which you’ll be able to drop a font file and see what languages are supported, however you need to drill right down to learn the way these instruments are figuring out language help. FontBook is extra lax than FontDrop! about when it thinks there’s English help, i.e., some fonts that do not present English help at Fontdrop! are listed by FontBook as having English language help.
Anyway, what I did is locate considered one of my third social gathering fonts that FontBook included in its English good assortment that additionally had comparatively few glyphs. This font has all of the characters in Unicode’s “Primary Latin” set plus Ä, Å, ä, å, Ö, ö and ¨ (that is A/a with a diaresis and circle, O/o with a diaresis, plus the diaresis itself). On fontdrop.information, this font reveals as having solely Zulu language help, however in FontBook it has extra, together with Cornish, English, Indonesian, Malay, Somali, Swahili and a bunch of others I’ve by no means heard of (Asu, Bemba, Bena, Chiga, Congo Swahili, Gusii, Kalenjin, Kinyarwanda, Luo, Luyia, Machame, Makhuwa-Meetto, Makonde, Morisyen, North Ndebele, Nyankole, Oromo, Rombo, Rundi, Rwa, Samburu, Sangu, Shambala, Shona, Soga,Taita, Teso, Vunjo).
I took considered one of my very own customized fonts, which is meant to have just a few glyphs, and added dummy glyphs as wanted for all the pieces in Primary Latin + the diaresis (figuring that the opposite characters won’t be wanted if I had the diaresis) and voilà – the font seems in FontBook’s English good assortment and can be utilized to annotate issues in Preview.
To make life sophisticated, I’ve acquired one other third social gathering font that FontBook put into the English good assortment that has solely the 26 letters (caps and lowercase), numbers and an asterisk, however for those who make a customized font that has all the pieces in Primary Latin and nothing else (so the letters, numbers and an asterisk plus a bunch of different stuff), FontBook says the one language supported is Zulu – go determine.
I made a take a look at font that had simply higher and decrease case letters, numbers and an asterisk and FontBook put my take a look at font into the English good assortment – however as I mentioned, a take a look at font with all the pieces in Primary Latin, which really has extra characters, did not go into the good assortment.
In fact, Apple might make life less complicated and make Preview capable of “present all fonts” the best way each different Mac app can, however…
BTW, if anybody is aware of of a web site that reveals what characters are wanted for what language help, I might like to learn about it.