A slightly more complex, but still very easy to use tool, to manage window size.
hotkey limited to up/down/left/right/fullscreen to just window size, but can work well with ultra-wide monitors with 1/2 and 1/3 split screen horizontally.
I have tried Div(workflow), both only do 1/2 height/width split screen. (learned a lot from it, thanks)
magnet(app) can do 1/3 split screen, but need to bind too many hotkeys.
It use applescript, so requires no dependency on macOS. But it has a slight lag after input.
Author: me
Main Page: https://github.com/nicholasxuu/alfred_workflow_window_resizer
Screenshot: (it's a hotkey only app)
Usage Demo: (Gif)