Learn Danish: Dommeren mangler dokumentationen angående erstatningen. - The judge lacks the documentation regarding the compensation.

angående translates to regarding or concerning. You can absolutely use vedrørende here with the exact same meaning. Both are present participles functioning as prepositions, and both are very common in formal, administrative, or legal contexts like this one.

The word angående ends in -nde. Does that mean it is acting as a verb here?

It originates from the verb at angå (to concern), and the -nde suffix forms the present participle, much like the English -ing in regarding. However, in this sentence it functions purely as a preposition of reference, linking dokumentationen to erstatningen.

How does the verb mangler work compared to the English missing?

English speakers often struggle with at mangle because Danish uses it actively. Instead of saying the judge is missing the documents, Danish says Dommeren mangler dokumentationen (the judge lacks the documents). If you just wanted to say the documentation is missing without saying who lacks it, you would say Dokumentationen mangler.

Why do we use the attached suffixes for dokumentationen and erstatningen instead of the separate word den?

As a quick refresher: Danish only uses the separate definite article (den, det, or de) when an adjective modifies the noun. Because there are no adjectives in front of the documentation or the compensation in this sentence, you must use the attached definite suffixes.