We can add the fonts to the fonts dropdown in addition to the existing basic fonts. To add 'Times New Roman' to the font names drop down-
ToolbarDropDown ddlFonts = (ToolbarDropDown)infraEditor.FindByKeyOrAction("FontName");
ddlFonts.Items.Add(new ToolbarDropDownItem("Times New Roman","Times New Roman"));
Similarly to add all the windows registered fonts-
ToolbarDropDown ddlFonts = (ToolbarDropDown)infraEditor.FindByKeyOrAction("FontName");
InstalledFontCollection fonts = new InstalledFontCollection();
foreach (FontFamily family in fonts.Families)
{
ddlFonts.Items.Add(new ToolbarDropDownItem(family.Name,family.Name));
}