I can solve this with a normal tie
But if I want the RH D4. to be Voice 1 in LH, I cannot move it up to RH stave. Is it possible? I would like to maintain correct voicing, and avoid slurs as “faux tie”.
It looks like if you want two notes in two different staves to be tied, they must belong to two different voices…
I thought that maybe in Engrave Mode it might be possible to move the notes individually, but they also both move together… That’s why I said it seems to be impossible to achieve what you want with a single voice.
A normally tied note is treated by Dorico as a single object. So a note tied across the staves must use different voices.
OK. Hopefully that could be improved in a future version (in Write Mode, where I think this modification belongs).
Why? The current logic delivers exactly what you need.
I don’t see it what way. A tied note is one thing, at which staff its “components” are placed is another.
As @Janus said, it is one thing. It does not have “components” as such. To treat them as “separate” parts is much like Solomon solving the question of who’s baby it was by cutting it in half! 
To split it between two staves, you literally have to create two distinct notes and tie them together”artificially”. (I do get what you’re saying but, unfortunately, Dorico holds a different paradigm and for it to do what you’re asking would break the coding for its normal structure.)
Like a single line in Illustrator has anchor points, I see a single tied note as having ‘anchor points’ for each note that is tied. You don’t draw 3 lines in Illustrator to form a “Z”, you draw one line with anchor points. The advantages are several.
True enough. I don’t know all the “underpinnings” in the code but I’m guessing they are independent of the note duration. (Maybe like the clothes on the baby?) But point taken! (I hope I didn’t offend….)
These are examples of the general differences between Write and Engrave. You can change the look of elements in Engrave, but not their semantic meaning.
Absolutely, you’re right!
But for me, some differences (with tied chains) are not entirely clear.
For example, in Engrave mode, you can: 1. use cross staff, 2. change a notehead, 3. change a note scale, 4. change a note color (as you say: only non-semantic things)
However, in a tied chain, only 2. and 4. are possible on independent notes.
1. and 3. will affect all the notes of the chain.
You know, seeing that S-shaped line between the two Ds, I see a slur and not a tie, particularly because of the position of the endpoints.
I think it would cause FAR less confusion - if the notes ARE effectively tied - to have them be in the same staff, either the upper one or the lower one.
That is one solution, but it would require “m.d.” and/or “hooks”* to show which hand plays what. I think the composer wanted to use this notation to make the use of hands clear.
(*) Pianists/organist usually pencil a large U or upside-down U to “move” notes to the “right hand”. Dorico doesn’t support it (yet?), and I’m not sure it’s a pretty solution either for a printed score.
I don’t even think hooks or text indications are necessary here.
A pianist will easily deduce the easiest and most logical way to perform this.
As I said, the way it is marked, with an S-shaped curve, leads to more questions and doubt as to the actual intended performance of the passage: is it a tie? or is it a slur? (as I said, to me it looks like a slur)
I’m saying this as someone who has been very comfortable as a pianist for the last 60 years.
just to let you know how I read this passage:
If the notes change hands, then they will be re-struck.
if it’s a tie, then the upper D would be played reflexively by the left hand.
So why not simply place it where it makes the most logical sense from a performance point of view?
You are probably correct in that a skilled pianist would solve many situations. I will make a note of it for the editor.
It could be that the ‘target group’ was ‘lesser-skilled’ performers. I don’t know the original edition’s “target group”. It can be difficult to decide how much help (fingering, stem directions, staff, …) to include. As Virgil Fox once wrote in a score IIRC (concerning registration of a piece), “If it sounds good: USE IT!”