Top 6 Swift window-manager Projects

Amethyst

61 12,850 4.2 Swift

Automatic tiling window manager for macOS à la xmonad.

Project mention: How to tile (auto-fit) all open windows on the screen? Example: If you have 8 windows open, you want to auto-fit all 8 windows on the same screen. What about 3rd party apps? | reddit.com/r/MacOS | 2023-05-25

This can be done through third party programs such as amethyst. It's not a native feature unless I am mistakened.
alt-tab-macos

156 7,478 8.4 Swift

Windows alt-tab on macOS

Project mention: What apps have you used to help transition from Windows to Mac? | reddit.com/r/MacOS | 2023-05-28
Appwrite

appwrite.io
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Appwrite - The Open Source Firebase alternative introduces iOS support. Appwrite is an open source backend server that helps you build native iOS applications much faster with realtime APIs for authentication, databases, files storage, cloud functions and much more!
later

9 1,131 4.2 Swift

Save all your Mac apps for later with one click 🖱️

Project mention: I created an app that launches your apps in the window layout you want | reddit.com/r/macapps | 2023-05-01

The fourth is Later, a simple and nicely designed app that allows you to close and reopen apps and docs. The project has been abandoned, but the dev has made it open source on GitHub, so the code can be reused.
Penc

3 1,014 0.0 Swift

Trackpad-oriented window manager for macOS

Project mention: 11 MacOS apps to increase productivity with trackpad | dev.to | 2023-01-10

Yet another window manager designed for trackpad usage. Double press and hold command key to activate Penc. Perform two-finger gestures to move or resize any window. Then release command key to take effect. Site: https://deniz.co/penc/ Price: free Source code: https://github.com/dgurkaynak/Penc
Memmon

1 84 10.0 Swift

A simple daemon that restores your window positions on external monitors.

Project mention: Multiple display monitors: app-window positions change after screen lock. How to fix? | reddit.com/r/MacOS | 2023-02-28

Per https://apple.stackexchange.com/a/428756/13179, Memmon has received high marks (one of the few if only apps/utils with recent apple.stackexchange.com reviews for this problem). I'm trying it out and will report back.
Assembl

1 60 7.3 Swift

An effortless window manager for macOS

Project mention: Asseml - The effortless window manager for macOS | reddit.com/r/coolgithubprojects | 2022-08-10

NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020). The latest post mention was on 2023-05-28.