When you hover your mouse cursor over the Maximize icon on an opened window, the Snap Layout menu appears. In this menu, you can select the desired layout to place your apps on your display. The Snap ...
In the coming months, Instagram is going to change that selection you see at the bottom of your app to home page, Reels, DMs, ...
Do you prefer customizing everything? The Vivaldi web browser now allows you to tweak the tab bar - any bar, actually! - to your heart's content.