SSIS Toolbox missing in Visual Studio 2017

I have installed the Data-Tier Application Framework and SQL Server Data Tools for VS 2017 . I created a solution then returned to it a week later and the SSIS toolbox had disappeared.

I opened the toolbox window using View -> Toolbox but it was empty.

To get the SSIS toolbox back, right-click on the SSIS design surface in the project and select SSIS Toolbox – hey presto! it reappears.