Placeholder in group Template not working with customResizeTool and rotateMultipleTool

I just read this in the custom tool you provided…It is likely that you will want to set the Part.resizeObjectName to refer to an element
_ inside your Part, rather than having this tool set the desiredSize of the whole part._
_ Otherwise a resizing after a rotation may cause the parts to sized a lot bigger than might be expected,_
_ because the desiredSize of a Part is always in document coordinates, not rotated._

So, I want to know where i have to set this PArt.resizeObjectName and if i set this property, will resizing work properly even after rotating the diagram?

Presumably you have seen that Part.resizeObjectName is indeed set in the Group template of that sample.

Have you read GoJS Tools -- Northwoods Software ?

One cannot rotate the diagram in GoJS.