Hide/toggle ui option

having a toggleable UI is extremely important for those who have smaller screen real estate. i find it especially useful when im doing homework and i have multiple windows open, one with a PDF of the textbook for the class, another with the homework open, etc.
(i believe) it would only take a few lines of code, as i make a duct tape hack for it in Firefox.
i loved this feature in vivaldi but they messed it up in a recent update, which made me start searching browsers. i found that brave was by and far the most performance browser, and having it fully open source is commendable. having this feature would be extremely beneficial to my, and many others’, workflow