Unfortunately VeriStand does not allow to add a custom tool to the Tool Launcher.
An alternative approach could be to embedd the custom tool in a VI and add such VI to the VeriStand Project files as follows:
- Right click on the .nivsprj item in the VeriStand Project Files tab of the Workspace
- Select "Add File"
- Navigate to the local folder containing the VI to be added to the VeriStand Project