No installation required, just download and run the executable for your operating system:
You may have to give permission before your operating system will run the executable:
chmod +x spatial-model-editor on linux, right-click open on macOS, “More info”->”Run anyway” on windows.
Note: on linux some additional system libraries are required that may not be installed by default. To install them:
sudo apt-get install libxcb-xinerama0
sudo yum install xcb-util-image xcb-util-keysyms xcb-util-renderutil xcb-util-wm