You can use Automator on macOS to create an application icon in your Applications folder that will launch a new instance of KiCad. Create a new Application workflow, then just put the single “open -n” (-n for new) command shown below into a “Run Shell Script” step and save as an application. I call mine KiCad New Instance so it sits right beside the KiCad directory in the Applications folder.
I also copy the icon from the KiCad application to this Automator application so it looks the same as the KiCad application. Get Info on theKiCad application, then select the icon in the top corner of the window and Cmd-C to copy it to the clipboard, then Get Info on the Automator application, select its icon in the top corner and Cmd-V to paste the copied icon.
Now you can launch an new instance whenever you want by double clicking the “KiCad New Instance” application.