vertical spacing issues v2.11.59

[Didi Kanjahn]

The vertical spacing of Lilypond works amzingly well when you have only one set
of scores and use the Title/Subtitle headers.

However, when I moved to using markup text instead of using the header, Lilypond
often does not succeed to use the vertical space vcery well. Even if the markup
text is less high than the headers were, it does not fit all the score onto the
same piece of paper any more and often leaves large spaces between the text and
the next staff. Using between-system-padding and between-system-space helps
some, but does not distribute space evenly and proportionally with the values
entered there. A between-system-padding = 1.7 may still leave 4cm of space below
the staves and may not give a decent space between staves and lyrics, a setting
of 1.8 brings one staff on the next page. Between-system-space increases the
space where there is only one line of lyrics (chorus), but not where there are
multiple, thus not distributing it evenly and again, small increases may cause a
staff to jump to the next page.
(13 with lyric size 7)

When using markup text for titles etc to combine several pieces of music in one
file the last one gets split up onto two pages almost regardless of its size. If
in this situation there was still 5cm of room on the bottom of the page (not the
last page) and I add a bottom-margin of 1.5cm Lilypond decides that there is not
enough room on the page anymore and moves all the staves onto the next page.

I have used annotate-spacing to see the spacing, but have zero idea of how to
make use of the findings. Where do I find that info and examples?

With the Cambodian script fonts that I use, Title and Subtitle of the headers
often have zero vertical spacing (line gap) and can touch, but I have not found
how I can increase this spacing by a little. All spacing commands and tweaks
seem to apply only to staves and text within a score.

How can I generally increase the linespacing between two lines of markup outside
the staves without adding a new line?