I have two questions concerning pianomusic:
How can I write this in dorico?
(1) how do I group the semiquaver triplets over two systems?
(2) how do I write slurs over two systems?
You can do it, absolutely. The voice between the staves could be a second voice of the first staff or the first of the lower staff. To create voices in Dorico, in write mode and with the caret active, input shift+V. Once it is done, you switch between the created voices inputing v.
Once the notes are input, you select the ones that you want to see “move” to the lower staff inputing m. If you have chosen the other solution and need to “move” the notes to the upper staff, press n.
To input slurs over whatever you want, click on the first note of the slur, cmd-click on the last and press s.
Hope it helps !
Thankyo very much for “m” and “n” to move to the pper or lower system
Thank you also for the “cmd-click” to mark what should have a common slur. I didn’t knew the “cmd” was necessary to combine groups of different voices.
Cmd-click is the usual method to select non-contiguous items in almost every program 
Go, Maestro! 
What ever am I doing wrong ?
You can see I am far from being a master at all:
My most important problems are
- the slurs are from looking so elegant like those of fratveno
- It is great to get such handlers to manipulate slurs with the mouse, immodest as I am , I would be most satisfied, if we would also get something like “curve-handlers” to manipulate the curve it self how it fits to the actual notation.)
- I really do not understand how to remove rests I do not want to see.
What I understand is theoretically, that the setting to begin or end a voice in a certain bar should erase the rests before or after ( I am even not that sure if I understood this principle right) But in my example I do have the problem that I do neither know always to which Voice a certain rest belong nor which the last note before or the next note after of this voice would be.
I also did not found yet the function to erase all unneeded rests which (if I understand right 1.1 should provide in the write menu (I am use the german version, perhaps I just do not know how you call in in german)
- It is great if there wold be a general function to erase all unnecessary rest (if ever I’ll be able to figure it out once) however I just wonder why there is not simply a “hide”-option in the propertytab of rest. This would make sense at least when there are not that much rests.
Thank you so far for your inspiring help. I am sure this will keep me in track to explore and understand all possibilities of dorico.
best
Steffen
To remove the rests you don’t want to see, simply select them and choose Edit > Remove Rests, and that will get rid of them.
OK, my mistake I looked in the write-menu. In so far the “rest”-problem is solved.
however, I would like to get the slurs as beautiful as fratveno has done. It would be great to understand, why this is currently not the case in my version.
- As you can see (in the updated version of the screenshot in my posting above), the slur seems to look a bit strange if I chose the last note of the second triplet as Endpoint and not the irst note after the second triplet.
- the slur seem to start in my version always frm the head of a note. this is not the case in fratvenos version. How did he does that?
I did a bit of manual adjustments (as I tried to replicate your example verbatim) but the slurs are straight forward to put right, provided you are in Engrave mode 
You can also flip them using the Properties panel… one additional tip: switch on “use optical spacing for beams between staves” in Layout Options/Note Spacing
Ah, Ok I confess I just was not yet aware enough of the different modes, just working in writemode I didn’t thought enough of th power of the engraver mode. Thank you.