Since Windows 7, you can easily resize your windows by dragging them against the left or right side of the screen.
However, since Windows 10, each time you stick a window against the left or right edge of the screen, Windows offers to stick one of the other windows in the remaining part of the screen.
Which can be annoying in the long run.

Here's how to disable this automatic suggestion on Windows 10.

1. Overview of Window docking on Windows 10
2. Disable suggestions when snapping a window
3. Anchor suggestions disabled

1. Overview of Window docking on Windows 10

As you can see, on Windows 10, when you drag a window against the left or right edge of your screen, a transparent rectangle appears to show you how your window will be resized.

Once you have resized the desired window, Windows 10 will prompt you to place one of your other windows in the remaining part of the screen.

If you click on one of the windows offered by Windows 10, it will take up the remaining space on your screen.

If you click in the empty space (where you see your desktop), then only the original window is resized and the others keep their current dimensions and places.

2. Disable suggestions when snapping a window

To prevent Windows 10 from always suggesting which window you want to place in the remaining screen space, open the Start menu and click: Settings.

Go to the "System" section.

Then, in the left column, click on: Multitasking.

As you can see, by default, all the options available under the "Dock windows" setting are checked.

Uncheck the box "When I snap a window, show what I can snap next to it".

3. Anchor suggestions disabled

Close the Windows 10 Settings window and move one of the windows to the left or right edge of your screen.

The desired window is resized to the desired side and nothing else happens.
Your other windows keep their current positions and sizes.