The method of loci (MOL)/memory palaces are a widely known mnemonic devices and enable memory artists impressive tasks (like memorizing several decks of cards, memorizing numbers etc.). Further MOL is featured in pop culture e.g. Sherlock Holmes, Hannibal Lector etc...

There is, to the best of my knowledge quite some research, which shows that MOL is working/useful for improved retention, especially when combined with spaced repetition.

It seems I have never seem real world examples of long term memory palaces/method of loci applications. It always seems like a short term crutch for cards, numbers, speeches, grocery lists, phone numbers, vocabulary or for test/exam preparation. For example it seems that in language learning, the MOL is for encoding some vocabulary and visiting it regularly, until it is committed to long term memory.

All examples I find in books about the method of loci are again only about having one location, a route of 10-N stations, and never about building/using mnemonic devices to organize bigger amounts of knowledge.

Are there any examples of people using the method of loci/memory palaces to organize for example their professional knowledge? Or of polyglots having/keeping memory palaces for language learning? Is there any research about long term usage of the method of loci?