Apparently requested since 2004, according to gHacks[1], but the oldest entry in Bugzilla I could find was from 2014[2].
However, that entry does reference a post from mozillaZine from 2004[3].
Though it's not really a request, but an addon that made it possible to change keyboard shortcuts back then.
Wow that’s a long time. I’m not familiar with Firefox as an organization but I would have thought them as being big enough or prominent enough to respond to feature requests more quickly. Or is that unreasonable?
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But they promoted they will not need one at any time, to extent they will never build one. There was only deno.land as a point to discover libraries or what community builds.
" ... one of the most interesting parts of Dieter's story is that he now looks back on his career with some regret. «If I had to do it over again, I would not want to be a designer,» he's said. «There are too many unnecessary products in this world.» Dieter has long been an advocate for the ideas of environmental consciousness and long-lasting products. He's dismayed by today's unsustainable world of over-consumption, where "design" has been reduced to a meaningless marketing buzzword."
"Rams is a design documentary, but it’s also a rumination on consumerism, materialism, and sustainability. Dieter's philosophy is about more than just design, it’s about a way to live. It’s about getting rid of distractions and visual clutter, and just living with what you need. The film features original music by pioneering musician and producer Brian Eno."
1: https://www.ghacks.net/2025/11/17/firefox-is-adding-support-...
2: https://bugzilla.mozilla.org/show_bug.cgi?id=972662
3: https://forums.mozillazine.org/viewtopic.php?f=48&t=72994