Hello!
Please have a look here:
With an example input from scratch, applying the factory default Notation Options and then changing just the option you’ve screenshotted, I get the result you want.
Is your example the result of a MusicXML import, or have you selected these notes and gone Edit > Beaming > Beam Together? Try selecting the passage, right-clicking (or going Edit) > Beaming > Reset Beaming.
If it is MusicXML, then for future reference it’s worth going to Preferences > MusicXML Import and unticking near enough everything. In this case it’s “Beam groups”, in the top section, that will have caused your problems. These settings only affect new MusicXML imports, though.
Thanks, yes its an import. I´ve tried to reset the beaming. Unfortunately the result generates more work (since its a 7/8-piece and the default beaming is totally different to the beaming the composer wants) than to reset it manually.
But, thanks pianoleo!, I have learned to reset beamings. 
You can influence the way that Dorico beams 7/8 bars by typing e.g. [2+2+1+2]/8 into the time signature popover. This doesn’t help you much if the beaming changes from bar to bar, though independent and hidden meter changes can still sometimes be quicker than changing all the beaming by hand.
Thanks!
Yes, I know this possibility. But as you mentioned the beaming changes quite often in this piece. 
Once you create a 7/8 beaming, it appears as an option in the right-hand time signature panel. You can create multiple beaming options and if you can remember which 7/8 represents which beaming option, you can switch back and forth by clicking the appropriate 7/8 preset.
EDIT: Whoops! I thought this used to work this way, but now apparently it no longer does, if it ever did.
