How to use SAssetDropTarget ?? I can't see it in Editor..

I’m developing a plugin and used the Unreal Engine wizard to create a base plugin. Now I want to use SAssetDropTarget and using the base plugin supplied by the wizard I did this:

Note: all the code is from the base plugin created by the unreal wizard EXCEPT the BOLD code

    SAssignNew(ToolkitWidget, SBorder)

            + SVerticalBox::Slot()
                .Text(LOCTEXT("HelperLabel", "Select some actors and move them around using buttons below"))
            + SVerticalBox::Slot()

**                    SNew(SAssetDropTarget)
                        ](const UObject* InObject) {
                            return true; // Trying..
                            //return InObject && InObject->IsA< UStaticMesh >();
                        ](UObject* InObject) {



I can’t see it in the editor… What am I missing here?
Thank you!

Box on AutoHeight() without visual elements inside will end up zero height.

Thank you Bruno Xavier! After your post I found that SAssetDropTarget is not a visual widget (it’s like a invisible box zone… that can be filled with other widgets) >_<
I found SContentReference and this is what I will use.