Setting application boundaries in KDE (a.k.a. the Linux DisplayFusion alternative)

Question

tl;dr

After all, is there a program/setting/script/tweak/voodoo to achieve a behaviour on Linux and KDE Plasma (or any other DE if not in KDE's case) similar to how DisplayFusion works on Windows, by defining the boundaries of what a "maximised" window is considered in each part of the display?

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Asking the "WH's"

I'm always bothered as to why such a phenomenal tool with so many practical applications does not seem to have a Linux counterpart (AlternativeTo's sole suggestion refers to a single minor feature in common, not the gist of it).

Given the flexibility of KDE Plasma, it only goes as far as creating virtual desktops through System Settings, but these virtual desktops are also "virtually" separated, making them impossible to be rendered in a single display. How this could be achieved in KDE Plasma (assuming it could be done)?

In Reddit, there are three posts (here, here and here) discussing alternatives to DisplayFusion in Linux, but they either:

• Tell users to set up a tiling window manager: not the aim here, since TWMs do not allow for a window "on top" of another, so 6 applications will create 6 windows (breaking the example pattern above);
• Use ARandR (see below).

Speaking of ARandR and XRandR, since most DEs run on top of X.org, there should be a way to achieve the DisplayFusion solution, if not directly through the DE, by tweaking X itself. But the videos I found on YouTube deal with people using XRandR to set up additional physical monitors for a TWM (manual setup). That also outputs to 2 physical monitors, 2 desktop areas to work on. How could one use XRandR to split the area of a single phyisical monitor into several boundaries?

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The long story

After moving definitely to Linux around one year ago, I have improved my QoL by a tremendous margin to the point I'm uncomfortable with Windows at this point. One thing that let me down though when I made the switch was the apparent lack of a DisplayFusion alternative, but as the months passed, I got used to it.

Having set up my workstation with a laptop solely displayed on an external ultrawide monitor, it has always been a hassle to plug anything other than this laptop given the lack of physical space around my desk. Lately, thoug, I have managed to plug my work laptop with Windows and installed DisplayFusion to work with it.

Now that I remember how much more useful this application is with my ultrawide monitor, I crave to implement a solution for my Linux desktop. However, how much I try, I don't seem to find anything (whether an application or a complex configuration) that remotely resembles what DisplayFusion can achieve. Is it even possible?

Information that could be useful on my case:

• Arch Linux;
• KDE Plasma 5.21.2;
• Setup comprised of a laptop and an external ultrawide monitor, with image output sent solely to the monitor (laptop lid is kept closed);
• xrandr output:

Screen 0: minimum 320 x 200, current 3840 x 1600, maximum 16384 x 16384
eDP-1 connected (normal left inverted right x axis y axis)
   1366x768      60.02 +
   1280x720      60.00    59.99    59.86    59.74  
   1024x768      60.04    60.00  
   960x720       60.00  
   928x696       60.05  
   896x672       60.01  
   1024x576      59.95    59.96    59.90    59.82  
   960x600       59.93    60.00  
   960x540       59.96    59.99    59.63    59.82  
   800x600       60.00    60.32    56.25  
   840x525       60.01    59.88  
   864x486       59.92    59.57  
   700x525       59.98  
   800x450       59.95    59.82  
   640x512       60.02  
   700x450       59.96    59.88  
   640x480       60.00    59.94  
   720x405       59.51    58.99  
   684x384       59.88    59.85  
   640x400       59.88    59.98  
   640x360       59.86    59.83    59.84    59.32  
   512x384       60.00  
   512x288       60.00    59.92  
   480x270       59.63    59.82  
   400x300       60.32    56.34  
   432x243       59.92    59.57  
   320x240       60.05  
   360x202       59.51    59.13  
   320x180       59.84    59.32  
VGA-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 connected primary 3840x1600+0+0 (normal left inverted right x axis y axis) 880mm x 367mm
   3840x1600     30.00* 
   2560x1080     60.00    59.94    59.98  
   1920x1080     60.00    60.00    50.00    59.94  
   1920x1080i    60.00    50.00    59.94  
   1680x1050     59.88  
   1280x1024     75.02    60.02  
   1440x900      59.90  
   1280x960      60.00  
   1280x800      59.91  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   720x576       50.00  
   720x480       60.00    59.94  
   720x480i      60.00    59.94  
   640x480       75.00    72.81    66.67    60.00    59.94  
   720x400       70.08  
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-2 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)

• hwinfo --short output

monitor:
                       Acer XR382CQK
                       AUO LCD Monitor
graphics card:
                       Acer Incorporated [ALI] GeForce GT 720M
                       Intel 3rd Gen Core processor Graphics Controller