Thank you very much, Doitsu.
This does the job.
For the sake of completeness, here are a couple more links with workarounds on the forum, that seem to cheat Kindle into believing that it's dealing with a default dictionary by changing ASINs. Which would be a possible (and only) solution in case of languages for which no free edited versions exist.
http://www.mobileread.mobi/forums/sh...27#post1845227
https://www.mobileread.com/forums/arc.../t-156694.html