Actually this is not a duplicate. For me this doesn't seem the same as "change the language of the spell checker from chrome extension code". Rather my issue is simply "have the possibility to add the vec language code to the list and attach my spell checker to it".
Anyway, if I can change the language of the spell checker via a chrome extension I think my issue is fulfilled. Any idea of when this will be possible?

Spellchecker is low priority right now, so interested engineers can pick up these issues and work on them in their spare time. It appears that no one is working on this issue right now, so don't expect it any time soon, please.

Spellchecker code is OS specific. Are there any operating systems where you would like to see this sooner rather than later?

Also note: On OSX or mobile devices, we cannot add dictionaries. 

I would like to see it on Windows platform.
Is there a way I can pick up the code and do the necessary modifications by myself and see them on production?

https://www.chromium.org/developers/how-tos/get-the-code
https://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/depot_tools_tutorial.html#_setting_up

Thank you!

I followed the page, download the source code, compiled it, and run it without problems.
I tried and tried to add my language to the language list in chrome://settings/languages without success.
I tried following every line where I know an existing language's name occurs (page https://cs.chromium.org/search/) and replicated them with my language without any success.
Anyone knows how can I add my language (in order to attach my .bdic to it)?

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot