Which tool do you recommend for keeping XLIFF (.xlf) translation files in sync?

I have an internationalized Angular project, using Angular's built-in i18n framework, where the translation files look like this:

messages.en.xlf

<trans-unit id="7380085404224719862" datatype="html">
   <source>Place a new request</source>
   <context-group purpose="location">
       <context context-type="sourcefile">src/app/components/foo.component.html</context>
       <context context-type="linenumber">13</context>
   </context-group>
</trans-unit>

messages.de.xlf

<trans-unit id="7380085404224719862" datatype="html">
   <source>Place a new request</source>
   <target>Einen neuen Antrag stellen</target>
   <context-group purpose="location">
      <context context-type="sourcefile">src/app/components/foo.component.html</context>
      <context context-type="linenumber">13</context>
   </context-group>
</trans-unit>

where messages.en.xlf is the source file that is automatically generated by the ng extract-i18n tool, and the other translation files such as messages.de.xlf are copies of that with translations added manually by a human translator.

There are 3 problems with this workflow as I understand it:

1. If I add or remove some lines in the beginning of foo.component.html then the line numbers referenced in the above files will change. For the source file this will happen automatically the next time I re-run the ng extract-i18n tool, but for the other translation files do I need to update them manually?
2. If I add a new text to the application, this will result in a new <trans-unit> in the source file, which I then need to manually copy to the other translation files.
3. Likewise, if I remove a text from the the application, I will need to manually remove the corresponding <trans-unit> from the other translation files.

It is very obvious that all 3 issues could (and should) be very easily automated by some tool, as syncing these files manually is extremely time consuming and error-prone. However I was shocked to see that IntelliJ does not seem to provide this functionality, and the same goes for all i18n/localization/xliff IntelliJ plugins I tried. Am I missing something here? Which tools do you use to keep your .xlf files in sync?

I am using ng-extract-i18n-merge and I'm very happy with how it works. It handles everything quite transparently and offers a lot of configuration. As soon as I change a translation id or content, the changes get reflected in all my xlf files, keeping them perfectly in sync.

This is of course a dev-dependency and not a plugin for intellij, but I guess that doesn't matter too much. If you need a small handy tool for editing translations, give TinyTranslator a go.