Hi, I would like to ask if it is possible to create a custom object in the Structure tree in SpaceClaim? Thank you.
No, there is not, but keep in mind the tree is only reflective of the created geometry, and not the operations like in a feature based CAD tool.
If you are looking for functionality that initiates an operation with basic user inputs, you can publish a script to a button and use the input helper class which is part of the built-in API.
Alternatively, you could use the ansys UI tool kit, or windows forms based UI creation to gather user inputs.