> a higher floor of effort juggling multiple separate GUI programs than going between tabs and panes in a terminal emulator.

Depends very much on your window manager. Tiling window managers such as Hyprland let you open multiple windows and it will automatically arrange them side-by-side. Want one of them to be 60% and the other 40%? No problem, there's a keyboard shortcut (configurable) for that. Have four windows open in a grid arrangement and want to switch between them? Just slide the mouse, no clicking needed so the movement can be as rough and imprecise as you want, OR if you don't want to take your hands off the keyboard then SUPER+arrow keys (also configurable) will move the focus to the next window in that direction. (And if you are in focus-follows-mouse mode then it also moves your mouse cursor to be in the middle of the focused window, so you won't lose window focus by accidentally bumping your mouse and moving it one pixel). Keyboard shortcuts for maximizing and un-maximizing windows, for throwing them onto other workspaces and switching between workspaces...

I throw windows around my screen all the time, and rarely take my hands off the keyboard to do it. It's the fastest, most flow-like window manager experience I've found yet.