Welcome to the forum, ezrudel. Once Dorico has calculated the staff spacing result based on the profile of things protruding above and below the staff, then making adjustments in Engrave mode won’t change that result: this is to ensure that the result is stable and doesn’t undo any other edits you have made unexpectedly. You might find that for a single-staff part layout, you get a more pleasing default result if you actually disable the feature that automatically avoids collisions between systems on the Vertical Spacing page of Layout Options. Often just setting a reasonable ideal distance between systems and letting vertical justification do its thing is sufficient.