I sometimes want to see the diff of what has changed only per line, but I find it uncomfortable to always move your hand to the mouse and click on the gutter marker. Is there a way to assign a shortcut to open that little diff window (as seen in the image)? I couldn't find an IntelliJ action that opens it.
That action is called Change Under Caret.
By default, no shortcut is assigned to it. You can find it with Find Action (Ctrl+Shift+A | ⇧⌘A).
You can also assign a shortcut to it right in this popup with Alt+Enter | ⌥⏎.
Other useful shortcuts:
Help documentation:
Use the keyboard shortcuts for Navigate:Navigate in File:Next Change/Previous Change
To make it even easier, modify the shortcut for that command to your liking in Preferences:Keymap.
