Hi, thanks for trying out the MacOS version. This is incredibly new to us, so we appreciate your feedback. First, check this guide under the "Loading the QSWAT+ plugin" heading and see if you can troubleshoot what could be going on there. Make sure you have QGIS 3.16.
If you will open either the installforme.sh or installforall.sh (whichever you used) in a text editor, you can see the location of SWAT+ Editor to launch it on its own.
Keep us posted with how it goes. Thanks!