Hi, sorry for the delay. The changes look good.
To fix the failing check, you need to add a change log entry to the CHANGELOG.md file.

To address your questions:

• I think most of the stanzas are covered now, with the exception of the stanzas from the config section, which I do not know if they're in a separate file or not.

  The documentation mentions that config stanzas can be used in dune-workspace. That means the syntax patterns need to be added to dune-workspace.json.

• I was not sure if I was allowed to make a separate rule in the file's repository for both the normal menhir stanza and the menhir stanza in env. I can add it if it's okay.

  That's a good idea.

• The documentation for the subst stanza seems to be incorrect, I think. It says that the subst stanza takes a <bool> as an argument, but it actually takes <enabled|disabled>. For example, the warnings stanza takes <enabled|disabled> and is documented as such. If you want, I can make a PR to fix this.

  I'm not very familiar with these specifics, but I think you're right. You can make a PR to correct the documentation if you wish.

• Another thing that I noticed is that the different TextMate grammar files have different formatting styles. This isn't that big of a deal, but it's something that I noticed.

  Our formatter for JSON files, Prettier, tends to preserve newlines. There may be some settings to make the formatting more consistent, but I agree with you that it's not a big deal.

• Should external_variant be added to the syntax highlighting? I didn't add it as it was an experimental feature removed in version 2.6 of dune, and there's no documentation for it in the dune docs anymore.

  I agree with your decision. There's little point in highlighting a removed feature, especially one that was experimental.

• I noticed that there is a variable.declaration.other.dune name and a variable.other.declaration.dune name in the syntax highlighting files. I don't know if this is intentional or not, and I do not know if there is a difference between the two. I tried both of them and they both seem to work the same way.

  I don't think it was intentional. I believe it's supposed to be variable.other.declaration.dune since that's closer to what other languages use.

• For the install stanza, the documentation only mentions 3 fields (files, section, package), but the syntax highlighting file is highlighting way more fields than that. I think there may have been a mistake with the executable fields, as there's a mention of the install stanza in the documentation for the executable stanza followed by the fields for the executable stanza. I'm not sure if this is a mistake or not, but I mentioned it just in case.

  There does seem to be some mistake here. I don't think it was a confusion with the executable fields though. The install stanza documentation includes a table that has most of the current fields. The problem is that the list in the table is supposed to represent values for the section field, not field names like our current interpretation.

Let me know if you have any further questions.