I just installed JS Switch on Nightly and clicked the Menu(burger) icon, then Customize, and was able to drag the JS Switch button into my toolbar.
(This does not address that it's crappy that icons that were in the addon bar don't, say, automatically get put into the toolbar or trigger a message notifying you how to get them back or anything, but oh well. EDIT: According to another reply this may not be the case with all addons, seems like some automagically get moved.)
(This does not address that it's crappy that icons that were in the addon bar don't, say, automatically get put into the toolbar or trigger a message notifying you how to get them back or anything, but oh well. EDIT: According to another reply this may not be the case with all addons, seems like some automagically get moved.)