You may try to modify a style or text to include Bold, Italic, Subscript or Superscript font attributes, and find that these options are not available.
Issues with bold and italic are due to a change in OS X support of font attributes (TrueFont). EndNote uses the Mac OS X font preference; if the font does not support bold or italics, you cannot use those styles in EndNote.
You will need to select a display font that supports bold and italic, such as Times New Roman or Verdana.
To select a different display font:
In EndNote, go to the EndNote X9 menu, select Preferences, and then select Display Fonts.
Under Display Fonts, change the General Display Font to the font of your choice. Again, we recommend Times New Roman or Verdana.
Save your changes, close the Preferences window, and try changing the font attributes of your style or text once again.
To use Subscript and Superscript in an output style, highlight the text you would like to change and go to the Edit > Font menu to select the attribute you would like to use.