It can be helpful to have a clearly-identifiable lock button for both the browser extensions and desktop apps. I use Firefox on my MacBook and I work at environments where I have to physically move away from my laptop ever so often, and have to move around a quite a lot. It'd be less fatiguing and (importantly) more secure if I could quickly lock my the desktop app and/or extension before moving away from my laptop. Just a little QoL feature that would be fantastic :-)