The functionality does not exist presently. However, with my experience of multi-lingual documents, I think you can work around it in a very convenient way.
Switching language manually for spell-checking is wrong, mainly for two reasons: it is a direct formatting instance (which will always play tricks on your back) and you may forgot to switch (or to remove an instance).
In an elaborate document, “styling” is used to semantically markup your text. Among the attributes of paragraph and character styles, there is one located in the
Font tab called Language.
When I write a full paragraph in a foreign language (a language different from the default language for document), I style it with a paragraph style derived from Text Body with language set for this language. Similarly, I have a character style with only the language set to format insertion of words in the other language inside a paragraph.
I also have a character style with language None to tag math variables, trademarks or computer jargon to eliminate them from spell-checking.
The inconvenience is to duplicate similar paragraph styles which differ only by their language, but I gain them in speed (and number of clicks) in selecting only the paragraph style either from the toolbar menu or the style sidepane. These styles are included in my custom template and are available for all my documents.
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