Hi Don,
The question with regard to disabling multi-selection has already been answered
here. The answer applies to the treeview component as well.
I'm afraid that showing the details of all selected products is not possible due to various technical reasons.
With the upcoming release of the Software Factory - 2019.1 - you can configure an extender to prevent multi-selection for both trees and grids. At this point, no custom extender is needed.
