I wish fiting systems into a page would be a bit easier and intuitive.
I would love to be able to just select systems and choose fit to page.
Then, I would fix whatever spacing problem I have between some staves with the system spacing tools.
I’m a bit going trough a nightmare here formating my first set of parts in Docico 
Best
Yan
There is a Make Into Frame button in the left panel of Engrave mode. Click the first thing you want on the page, then Cmd/Ctrl+click the last thing you want on the page, then click Make Into Frame.
For parts, the easiest way to set the systems into pages is: set an appropriate value for the gap between systems in Layout Options > Vertical Spacing. I usually reduce the value to about 7 spaces.
For multi-flow works, I turn on Flow Headings and let flows run across pages. Then I just set a few Frame Breaks where I need to, for good page turns and to get whole movements on a spread. If you want to force more systems on a page than the default, use Make Into Frame (or apply two Frame Breaks, and click on “Wait for next Frame Break” in the properties pane of the first one.)
If the music is simple, you can set bars per system and systems per page in Layout Options.
I can create a set of beautiful instrumental parts in minutes with Dorico. The trick, I think is not to do too much: let Dorico do it.
Note that once you’ve done what Leo describes, there are frame breaks applied, that appear as signposts. In write mode, you can move those breaks like any other object, using alt-left/right arrow (value of rhythmic grid). I find this a very powerful way to change my layout once everything is done.
ok thanks…
I’m getting there slowly.
I realise how hard it is to change habits after 30 years with the same software…
Best
Yan