In the interests of fairness, since I grumble about Firefox so much, now a grumble about Vivaldi for android:

if I click on bookmarks, I want the bookmarks UI to fill the whole screen, not a slider that fills 1/2 or 1/3 the screen.

I guess whoever programmed this must feel clever they got it to work, but its even more clever to not implement a UI element that has makes the user experience worse.

Till the end of time, there is not going to be a situation where someone wants to look at a 3x5cm sliver of bookmarks with one eye while they look at a 3x5cm sliver of previous webpage with the other eye. Like, how much cocaine do these people snort that anyone decided that's a good idea?