The Note gramplet is a data entry, similar to the DataEntryGramplet. This gramplet will edit the first note of type Person Note for the active person. Like the Data Entry Gramplet, once you begin editing a note, it won't leave the current person until you save or abort.
Note that you must save your changes before closing gramps, or your changes will be lost.
You can download this plugin by following the directions at Third-party Plugins.