You can move the left and right margins of each individual staff system with the Layout tool, so they don’t align horizontally with the page margins. Local margins are saved as part of the current score set, allowing different settings for each score set.
In Page view, choose the following settings from the Score Editor’s View > Page Display Options submenu:
Print View
Show Margins
Click-hold (with the Layout tool) a little inside the beginning or end of the staff, then drag to the left or right.

During this process, Left or Right Staff Margin appears in the help tag.
Note: When altering margins, the number of bars per line adapts automatically (unless you have manually adjusted line breaks beforehand). If the line is shortened, bars may be moved down to the next line, depending on the Spacing parameters in the Global pane of the Score project settings. (See Global Score settings.)
Double-click at the end (or beginning) of the margin with the Layout tool.
Choose Layout > Reset Line Layout from the Score Editor menu bar.