I could try out the translation for Croatian!

[KLiK]

Which can also be understood in most of ex-YU, so: Croatia, Bosnia & Hercegovina, Montenegro, Serbia, Kosovo...just let me know & mail me a form to translate! 

[fred]

Which can also be understood in most of ex-YU, so: Croatia, Bosnia & Hercegovina, Montenegro, Serbia, Kosovo...just let me know & mail me a form to translate! 

Great, you already have everything you need.
Go to C:\Program Files\eFMer\TThrottle\lang
Open languages.xml with a simple text editor like the build in notepad.

I personally like notepad++ https://notepad-plus-plus.org/

Add you language tag to this file like this
   <Language>
      <NameEnglish>new</NameEnglish>
      <Name>new in your own language</Name>
      <Id>1033 this number is shown in the TThrottle log: Language: User: </Id>
   </Language>

Now copy TThrottle_ENU.ttlang to TThrottle_HRV.ttlang

HRV depends on the 4 digit number probably something from this list: http://www.the-localization-tool.com/language-codes-mfc/

If you got it wrong, you will get an error message about a missing file with the correct name.

[KLiK]

Finally made 1st version of Croatian translation of a file. As there is no github, so adding it on server here:

https://file.io/rhQUt7Kor31A

This should last for a year to be downloaded.

[fred]

The download is already gone, you can use the email address that is mentioned in the program.