As a starter:
In Delphi, there is a need for a design-time stub component used from the Delphi IDE form designer and the runtime component. The design-time stub components are in the "Component Library Source" folder while the runtime component source code is in the "Core Source" folder.
In VSC, the designer is a webview, hence, runtime & designtime code are the same. You should be able to use the same code in Core Source folder as you used in VSC and what you need to do is add the design-time stub class in Component Library Source and register it with the IDE.