Thankfully you can set a hotcorner to minimize the current window in Settings >> Desktop >> Hotcorners.
However, If you're not on elementary, you won't have the option to set a corner to minimize the current window, even if hotcorners are available to do other actions.
To enable a hotcorner to minimize the current window in another distro, you just have to do the following:
1. Specify a keyboard shortcut in your System Settings for Minimize Window (eg: Ctrl+Shift+m).
2. Install xdotool;
3. Specify a hotcorner to Run a command;
4. Enter xdotool key Ctrl+Shift+m in the command box
Enjoy your hotcorner to minimize current window!!