You can find options for the project-wide appearance and position of string indicators on the String Indicators page in Engraving Options.
The options on the String Indicators page allow you to change the appearance of open string indicators, the size of string indicators inside the staff, whether their notehead-relative position should change if left-hand fingerings are present, and the exact positions of string indicators relative to each other and other items.
The options are accompanied by diagrams to help you visualize how they affect the appearance of your music.