How can I set a fixed distance between the staves for each voice?

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In the example below, I am using a template.
I would now like to set this template so that each voice has a fixed spacing between the staves.
However, this fixed spacing should be different for trumpet parts than for alto parts, for example.
In addition, all lines should not always be automatically distributed evenly on one page, as this would lead to unnaturally large line spacing for titles with few lines of notes.
Until now, I could only achieve the desired result by laboriously correcting all the stave spacing in each voice individually.
I have not been able to find out how to set this globally.
Can anyone help me?

Attachment: 1. the project. 2. the corresponding template. 3. a screenshot of the trumpet part of this project.
E64 Miljö 23 - För 1 Naach.dorico (1.0 MB)
V E.dorico (1005.6 KB)

[Vadian]

You can set the spacing globally per layout(!) in the Layout Options.

First of all remove all manual changes by resetting the Staff Spacing layout in Engrave Mode.
Then disable Casting Off Fixed number of systems per frame in Staves and Systems.
With Vertical Spacing > Inter-system gap you can control the number of systems per frame and further down in Vertical Justification you can control whether a few lines of notes are spaced evenly on one page or not

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Thank you!
This answer was precise and comprehensive! It helped me a lot.