How to control the diagram elements based on a certiain condition?

[atejshee-tibco]

I want to design a project, wherein, the diagram elements should be added/edited conditionally, i.e. one diagram element is dependent on some other diagram element.

For example:

1. Initially, the Tool Palette will contain some bare minimum elements that the user could add
2. Based on what element the user adds to the canvas, couple of other element names should get visible on the Tool Palette that the user could further add to the canvas

How can we achieve this conditional control over the diagram elements?