I'm in crunch mode doing the internationalization and localization of my spreadsheet engine. This is a rabbit hole and a nightmare in Excel, so a big opportunity for us to get this right.
This is the PR: https://github.com/ironcalc/IronCalc/pull/616
Feel free to comment and destroy it!
You can test it in: https://testing.ironcalc.com
Glad to see you're doing this! I was wondering if the currency button could be changed. Defaulting to Euro is fine, but being able to switch that shortcut would be handy.