I see that the Trimble Connect Visualizer have button inside the Trimble Connect Desktop Application.
How to make add-in button in Trimble Connect Desktop using api? How to make child window or how to add panel with my plugin?
If there is no way then my proposition is to add this in next api release.
I asked the same question before, the answer is no. Custermization of TCD can be executed from external only. It means we need write separate application called/connect with TCD and execute function.