Have you had a look at EurKey layout? I, too, have to switch between English, German and Italian and I found it to be great.
https://eurkey.steffen.bruentjen.eu/?lang=de
This is very interesting, but WestEurKey would have been a more suitable name, as there is no support for Slavic languages.
alt Hacker News
This is very interesting, but WestEurKey would have been a more suitable name, as there is no support for Slavic languages.