You can add an arbitrary number of tabs to the entry editor. These will be present for all entry types. To customize these tabs, go to Options → Preferences → Custom editor tabs.
You specify one tab on each line. The line should start with the name of the tab, followed by a colon (:), and the fields it should contain, separated by semicolons (;).
will give one tab named "General" containing the fields url, keywords, doi and pdf, and another tab named "Abstract" containing the fields abstract and annote.