It was right in front of me on the Windows Installer Deployment page, with bold an everything.
In Visual Studio, create an InstallShield LE project from the New
Project dialog box. Once created, select the new project and then click the
InstallShield LE option on the Visual Studio menu bar and choose
Visual Studio Deployment Project Import Wizard.
I was looking too hard for an external “importing tool”.
For my setup I found it worked best to pull in the other project outputs if I chose “Add to solution” when creating the new ISLE Setup and Deployment “Other” project.