You can highly customize your dashboard menus and their submenus using the menu settings. Three main options available are the Menu editor, Settings and Styles.
In the menu editor pick the exact menu item or the submenu item you want to modify. Things you can customize:
This tab allows for customization of the overall menu structure and appearance in the WordPress admin area.
Menu Type: Pick whether you want a Vertical menu (traditional WordPress layout) or Horizontal menu (menu across the top of the screen)
Menu Mode =>
Icon Style: Default icons or rounded icons (Only available for Folded menu mode)
Sub Menu Style =>
User Info =>
Menu Item Style: Pick from Icon Only, Text Only or Both to determine how menu items are displayed in the horizontal layout
Dropdown Toggle Icon: Controls the visibility of dropdown icons for menu items with submenus
Top Menu Links: When enabled, allows parent/top-level menu items to be clickable
Bubble Icon: Controls the visibility of update or plugin notification bubble icons
Break Long Lists: When enabled, it breaks menu lines if the main menu gets too long for the screen width
Font Settings: This section likely allows you to change the font family, size, and weight of your menu text.
Text Transform: Options to control capitalization (uppercase, lowercase, etc.)
Font Size: Set the font size of your menu text.
Line Height: Adjust the spacing between lines of text in your menu.
Letter Spacing: Control the spacing between letters in your menu text.
Menu Width: Adjust the width of the admin menu.
Menu Wrapper Padding: Add padding around the entire menu. Padding creates a buffer between the edge of the menu and its content. You can set padding for the top, right, bottom, and left sides of the menu wrapper.
Parent Menu Horizontal Padding: Control the padding on the left and right side of the parent menu items (typically the top level menu items).
Sub Menu Wrapper Padding: Set padding around the sub menus (menus that dropdown from parent menus). You can set padding for the top, right, bottom, and left sides of the sub menu wrapper.
Sub Menu Vertical Padding: Control the padding above and below sub menu items.
Parent Menu Colors => Control the colors of the main menu bar, including:
Sub Menu Colors => Control the colors of the dropdown sub menus:
Notification Colors => Control the colors of any notification elements within the menu, such as badges or icons.