Icon for HTTPS-Everywhere can't be added to Add-on Toolbar

HTTPS-Everywhere 3.4.2 Firefox ESR 17.0.9 Slackware64 14.0

To reproduce:

• right click on the add-on toolbar to open the popup menu
• click Customize
• a window will open, containing icons related to misc Firefox actions or to Firefox add-ons
• there's no icon for HTTPS-Everywhere

Note: when HTTPS-Everywhere gets installed - it adds an icon to the Navigation Toolbar only. This is inconvenient for me because my Navigation Toolbar is always hidden (I am using the Pentadactyl addon). Being able to have a HTTPS-Everywhere icon in the Add-ons Toolbar would be very handy.