Hammerspoon

Hammerspoon is a Lua interpreter with the whole Mac wired into it. Its modules reach windows and spaces, hotkeys, the menu bar, WiFi, USB, displays, audio devices, the clipboard, HTTP requests and a good deal more. You edit ~/.hammerspoon/init.lua, reload, and the machine behaves the way you described: a hotkey layer that throws windows into thirds, a rule that sends Slack to the second monitor the moment it is plugged in, a menu bar item showing whatever number you actually care about.

The catch is not hidden — it is the premise. There is no settings window, no rule builder, no list of checkboxes. If writing code is a chore rather than the appeal, nothing here will be enjoyable, and the first genuinely useful config takes a couple of sittings with the documentation and other people's dotfiles.

It has been MIT licensed and community maintained since 2014. Support is GitHub issues, which works better than it sounds because the API documentation is unusually thorough for a project with no company behind it.

Someone who wants tiling and nothing more should install Rectangle or Amethyst and be finished in five minutes. Hammerspoon earns its keep when your idea of a good setup is specific enough that no shipping app contains it.