The spacing in the Part Navigator and other navigators appears excessive for unknown reason.
Solution This type of display format is indicative of the user applying a "Touch" type of role intended for use with touch screen or touch pads.
Go to Roles --> Presentation panel and select "Default" to reset the role from "Touch" back to "Default" type intended for typical mouse cursor interaction.
Notes and References
Hardware/Software Configuration Platform: INTL64
OS Version: 764