I really need the feature to switch between the German and English spelling dictionary on a regular basis.
At least it would be a fast - I know, not the best - solution to be able to switch between different spelling dictionaries using a dropdown in the tool menu and additional short cuts for this!
If auto detecting the active used language may be hard to implement, switching the language using a tool menu should definitely very easy!
Ok, forget about my comment! After searching more, I found the hint about using the right click menu! Button to quickly change spell checker language - #3 by Gary