Safety Button Needs Manual Installation Rated 4 out of 5 stars
Other reviewers have reported that the "Safety" button (one of the most valuable aspects of this add-on) is not visible on the toolbar even when it is a checked selection on the toolbar tab of the options menu. I had the same experience but a little exploration paid off.
If you select the "Safety" button but do not see it on the LinkExtend toolbar, close LinkExtend options menu and right click on the Firefox toolbar and select "Customize". In the large box containing the unused buttons, you should find the Safety button. It will be easier to identify if you had checked the LinkExtend toolbar option to display the toolbar button text. Drag the Safety button to where you want it, either onto the LinkExtend toolbar or onto the Firefox toolbar.
If you do the latter, and don't want to use the LinkExtend toolbar and search function, you can even disable the LinkExtend toolbar and the Safety button will still function the same way as if you had installed it on the LinkExtend toolbar. Problem solved.