Support Adding Workflow Activities to Toolbox Using Toolbox Controls Installer
Third-party builders of workflow activities (like for TFS Build) would like to be able to add their workflow activities to the Workflow Designer Toolbox by either having end users install our activity package using a VSIX deployment (using the Visual Studio Gallery) or by an MSI Installer.
This process would be similar to the way other third-party component vendors are able to add to the toolbox for WinForms, ASP.NET, Silverilght, WPF, etc. controls. We would like the same functionality for Workflow Activities.
Original Forum Post with more details: http://social.msdn.microsoft.com/Forums/en-US/vsx/thread/410242a8-42ac-42b6-8fcf-08088bd5b31a
Have you tried the option posted recently on the forum: