In the Atoms UI, you can also create new Behaviour Modules, but you will need some Python knowledge.
As soon as you click on the "Add" button a script template will be added and registered. Comments for each method explain briefly what you can do at each stage.
Please note that your Behaviour Modules will be running in Atoms, but you will also be able to use your 3D application Python modules (i.e. maya.cmds, hou).
Please refer to the python section to know more about how to create Behaviour Modules.
For a full list of available behaviour modules please check this section.