The “right” way to tag a sequence as belonging to a language is through styles. The paragraph style defines the principal language. Since in the majority of cases there is a “principal language” representing the majority of the document, you can modify Default Style paragraph style language in its
Before you type a word or sentence in another language, you activate a character style setting this particular language. The character style can be associated with a keyboard shortcut so that you don’t need to grab the mouse to set the style.
A shortcoming of this approach comes from the present impossibility to set several character styles on a run of character (e.g. to add Emphasis). There is an experimental feature to do so, but it is not reliable and causes trouble in the document.
When I deal with multi-lingual documents, I don’t switch my keyboard language because there is only one key marking. Consequently, switching does not make sense in my case. When necessary, I prefer to customise second- or third-level character mapping to access the diacritics or national characters at a mnemotechnic position (at least for me considering the key layout and my notion of “mnemotechnic”).