Piano after MusicXML Import

I cannot edit the lower stave in the piano notation in pieces that I habe Importet via MusicXML or Midi.
When I start without Import and Setup the Piano, everything is fine. Inserting new Notes is only possible in the higher stave!?
Any suggestions? In the attached Picture You can see, what happens when I put the Notes an Octave low

I can tell you there’s something wrong in your system or in the way you use Dorico. But just to make sure it’s not the second thing, can you show the caret in the lower staff ? Normally, if it shows on the upper staff, you should be able to make it go on the low staff with the descending arrow. And then, you should be able to input notes…
What software do you use to export the XML files ?

Thanks for Your reply. The descending arrow moves the notes down but not into the lower system. MusicXML or midi is created with cubase 9.5. Afer Import everything looks fine, but I cannot edit…
Perhaps the red rest indicates that there may be a 2nd voice, but I dont know how to delete a second voice.

You move notes by selecting them and pressing alt-arrow (there is no other way, as far as I know). I was just talking about moving the caret (the big vertical bar that shows in note input) with the arrow (no key modifier implied)
If you choose (in view menu) to see voices colors, then you’ll see which rest and note belongs to the same voice…
The top staff and the low staff of the piano have their own voices, that’s the reason the notes do not go directly from the right hand staff to the left one just by changing the pitch. You can still use the m and n keys to make right hand stuff go to the lower staff and vice versa. Is that what you were looking for?

Hallo MarLarcher,
You did it. I didn’t know the keys m and n. Now it works. Thanks a lot.