There is no Reset property to galleries that when toggled will reset the selection to the Default item.
This is strange since Reset is present for example in text inputs and other controls that also have a Default property.
Please add the Reset property to galleries.
The reset functionality has been added to the Gallery control. To reset a gallery, simply call Reset(GalleryInstanceName)
Note that this will reset the gallery to its initial state, but will not recursively reset all the children of gallery.