[JulienRbrt]

I personally still have the "Subscribe" icon (Firefox 59). I had to move it from "Customize" to my toolbar but it is definitely there.

[lunchables]

Thanks for the tip, I just added it back.

[itakedrugs]

it used to be in plain view all the time (maybe 10 versions ago, I don't remember exactly)

[itakedrugs]

it was in the address bar, too: http://screenshots.oldapps.com/3/large_87_Firefox%201.5.0.12...