After a learning curve, and a trip down userChrome.css editing... I have arrived at:

#navigator-toolbox {
  max-height: 2px;
  overflow: hidden;
  transition: ease all 2s;
}

#navigator-toolbox:hover {
  max-height: 100vh;
  animation: 0s pop-in;
  animation-fill-mode: both;
  animation-delay: 2s;
}

@keyframes pop-in {
  from {overflow: hidden}
  to {overflow: unset}
}

You can mess with the transition speed and pixel height for your own preferences.

Thank you to Wesley Branton

Unfortunately userChrome.css is outside the scope of Firefox forum end user help and using it would mean the creator of the css edits would be the one to provide support for the css your using here.

Mozilla set up a new site for product idea submissions, if you want to pitch this one:

https://connect.mozilla.org/t5/ideas/idb-p/ideas

Dropa, exactly... I couldn't find a way to do what I wanted 'officially'. This is a bandaid, temporary fix, that also demonstrates the exact thing I was looking for

If you want to hide the menu bar you could also simply press F11 on your keyboard. If this was not the answer to your question, I would ask you to correct me.

This does not answer my question :) I am trying to do this withOUT using the 'Fullscreen' ability.

This does not answer my question :) I am trying to do this withOUT using the 'Fullscreen' ability.

We are very sorry that we could not help you, SupportGB is based on videos, answers and questions from the Internet and is not personal to the question to cut, nevertheless, it often agrees. We would be pleased if you could describe your question in detail so that we can answer you individually.

For reference:

• /questions/1284841 autohide everything when not hovered anywhere on browser