Hvad er forskellen mellem "sid ned" og "sæt dig ned"?
There is no difference, and both are used in common speech. The latter literally means "set/put yourself down".
The tooltips offer "sit" as a translation for "sid ned" but it is not accepted as the answer.
...is it just me, or is her accent uniquely difficult to understand in this one?
Sæt dig her ved mig.