Update 20.0.1 Rated 5 out of 5 stars

Same issue, choices disappear from Add-On bar, but still available in menu and context menu.

This review is for a previous version of the add-on ( 

As I wrote in version information I removed the code to show it by the options panel.

You can move the button in the addon bar by using the standard customize of firefox.

Thanks for your report.