I run Dorico Pro 5.1 under Windows 11 and want to condense two lines of music into one:
The justification threshold you’re referring to is vertical justification - it’s about spreading the systems on each page so that they fill the full height of the page, rather than having a larger margin at the bottom of the page.
In Engrave mode can you see percentage values at the right edge of each system? I’m guessing that while the first system has quite a low value, the value to the right of the first system plus the value of the second system would be greater than 100%, so Dorico’s splitting the music to two systems
You can brute force it by selecting something in bar 63 (in Engrave mode) and typing , (comma), or by selecting the System Break at bar 31 and setting it to Wait for next system break in the Engrave mode properties panel.
You can get tighter spacing globally by going to Library > Layout Options > Note Spacing and reducing the Default space for crotchet/quarter note from 4 to, say, 3.5. Or you can change these values locally, from any point in the music, by selecting something on the page in Engrave mode and going Engrave > Note Spacing Change and altering the same value in there. This will take effect from that point to the end of the Flow, or to the next Note Spacing Change - whichever comes first.
