I would have thought you’d need to reduce the crotchet value to something considerably lower than 2.5 spaces. Also, by default Dorico’s margins are wider than Sibelius’s, and you have staff labels showing on every system in the Dorico project.
The only things I’ve changed are
Layout Options > Note Spacing > Default space for a crotchet/quarter: 2 spaces.
Engraving Options > Notes > Noteheads > Appearance of double whole note (breve) noteheads: Round (not that this makes any difference to spacing).
The easiest way to break a system mid-flow is to use Shift-R Coda Enter. There are properties to remove the visible coda marking.
(Please excuse likely F# typo towards the end of bar 2.)
Do you mean the red time signature signposts? Each bar seems to be a different length, so the barlines are effectively non-default (not defined by the opening meter). I’m not sure I quite understand the convention here, but maybe you meant for bars 3 and, ahem, 3, to be a single bar with a system break halfway through it.
The bar lines are original. Thus bars 1 and 2 are the same length, and bars 3 and 4 are half that length. Bar 5 is again the same length as bar 1. So why cannot I get bar 1 to take up the same horizontal space as bars 2 and 5? (I have no idea why there are two bar 3s in your version!)
I don’t know what your staff size or margins look like, but it’s almost definitely that there isn’t space for (the entirety of) bar 2 to fit alongside bar 1 on a short system (short because of the full staff label.
I turned the note spacing crotchet value down to 2 spaces.
(I do know why there are two bar 3s; it’s to do with the way I added the non-standard barline.)
I am trying to have to avoid “make into system”, which would be needed about 50 times in this piece; but rather to find a setting that I can use as a default for music that is based on white notes, as this is. (I have a lot of other similar pieces to do!)
I had turned off staff labels in Sibelius, and not realised that they returned in Dorico – thanks!
Page margins are 14.96. Staff size is 6.5mm. Page size is A4 .
It seems that there is no way of explicitly setting the space of any notes longer than a minim, unless I am (again!) missing something.
More by good luck than by competence, I have made improvements. The proportions of the lengths of the bars are now better for some reason. I used the fake pick-up method for the time signature. Now I need to remove a lot of the vertical space surrounding the systems, and document how I did this (because I know I shall not be able to remember).
I am not happy with the design of the Long (at the end): it lacks gravitas in comparison with the breve. The Sibelius example (at the top of this thread) is much better, in my opinion.
For vertical spacing, the “ideal gaps” are used unless the page is vertically justified. If you don’t want it vertically justified, and instead only to use the “ideal gaps” as set, increase the threshold for vertical justification to e.g. 99% (meaning only when the page/frame is calculated to be more than 99% full will it justify vertically).