Is there a way to make a Placeholder stretch horizontally to the width of its parent Group?
Setting the Placeholder’s stretch property to go.GraphObject.Horizontal doesn’t seem to have any effect. Should this be working at all? or only under certain conditions?
It entirely depends on the kind of Panel that it is in.
http://gojs.net/latest/intro/panels.html
Not all panels respect the concept of stretch, and not for all objects in the panels.
If you have a mockup of what you’re trying to do, perhaps I can suggest an appropriate group template.