In the link below, you can see that manual note spacing jumps dramatically when the system is 100% full. I’m using Alt-arrow to get a small change, but I get a big one (too big).
It’s really common in hymnals to have systems that are overfull. Generally I find Dorico handles full systems beautifully, but this is one case that is difficult to work around. Could this behavior be improved so when systems are right at 100%, they don’t suddenly jump?