TCAdefaults.pages.backend_layout not working for pages created via drag and drop
Most may not need such default, because they use backend_layout_next_level. Sometimes, however, it can be very helpful to disable backend_layout_next_level by hiding the field ( TCEFORM.pages.backend_layout_next_level.disabled = 1 ) and rather assign each page its own backend_layout. This way you can save slide queries and use very simple conditions like [page["backend_layout"] == 'pagets__home'].
The following does already work when a page is created via context menu (click on existing page: "More options" > "Create new wizard”):
TCAdefaults.pages.backend_layout = pagets__default
If a page is created by drag and drop of the page-type-icon, this default backend_layout will unfortunately not be saved, so far.