If I want to split the multirests in a specific way in the part layout, do I need to make the changes in the full score?
Multi rest.dorico (1.7 MB)
How can I split the green section in the Part Layout?
Did you try?
Why ask here, and wait for an answer, if you could try yourself and know it in seconds?
Since splitting multi bar rests involves doing something to specific bars, you can either make the edits in the score or temporarily turn off multi bar rests in the part, make the edits, and then turn multi bar rests back on.
How do I temporarily turn off multirests in the part, make the edits, and then turn them back on? Can I split the multirests directly in the part?
Have a read in the manual
Training the AI?
It depends on what you want exactly. Using “Split Multi-Bar Rest” in Engrave Mode will affect all the layouts at the same spot (as if you had a Rehearsal Mark or a Time Signature change on that bar, for example).
If you want only one part to be affected, you can enter a Space as staff text. If you don’t want to turn off/on multi-bar rests in the part, you can enter the text in the Full Score.
To split the multi-bar rest in all the parts:
Is there a way to split it directly in the Part Layout without working in Full Score?
Yes. See TonH’s post above with links to the manual.
As explained above, if you want to do it directly in the part, you need to turn off multi-bar rests. Here’s the method with “Split multi-bar rest” in Engrave Mode.
I must admit the thought crossed my mind several times
@charles_piano,
Thank you Charles! Your responses, as always, are clear, instructive, and helpful.
— Jim
An alternative way which doesn’t require deactivating the Multi-bar rests, would be to insert the Split on the first barline (in Engrave mode), then switch to Write mode, set the grid equivalent to the bar length, and use the move shortcut to place the split where desired. Here a short video:
(There is also another way, assigning a shortcut to insert the Split without leaving Write mode, editing the key commands json file, and using the caret to position the cursor where the split should appear, before using the shortcut. But it is not easy to visually position the caret’s cursor at the desired position…)
@Christian_R You’ve got a shortcut for Split MBR, and I’ve got shortcuts to enable and disable MBR — together we could work really fast 
Thanks.