It happened that the content scrolled to the right (I don't know exactly what I did), but now I cannot scroll it back to the left - I don't see the content anymore correctly:

Even moving with the cursor (in both windows) and editing the entries did not scroll them into view.
What to do? Should be possible...
Only closing the App and restarting it did solve the problem.
Debug version of MM (portable) 5.1.0.2832 on Win10-PC.