The instrument designation in the layout of the score is as I would like it. With the designation Trumpet Eb.
But in the single voice comes e.g.: Clarinet (E Flat). I have tried all possible settings and find how to make this setting correctly.
Thanks for the support*
You can edit the name of the layout in the Layouts panel in Setup mode. You can use the token {@flat@} in the name of the layout to produce a proper flat accidental.
There are descriptions of the different names linked to instruments/players and where they’re used on this page:
If your first screenshot was to the left of staves in the score, that’s a staff label – it uses the instrument’s name.
The second screenshot is from the top left of part layouts – that uses the layout name.