I just tried this in a recent build, and deleting all the content and saving a page layout puts this in the file:
(page_layout (setup (textsize 1.5 1.5)(linewidth 0.15)(textlinewidth 0.15) (left_margin 10)(right_margin 10)(top_margin 10)(bottom_margin 10)) )
which seems to be enough to keep Kicad from thinking it's empty (at least I still get no content when I open it).
I just tried this in a recent build, and deleting all the content and saving a page layout puts this in the file:
(page_layout
(setup (textsize 1.5 1.5)(linewidth 0.15)(textlinewidth 0.15)
(left_margin 10)(right_margin 10)(top_margin 10)(bottom_margin 10))
)
which seems to be enough to keep Kicad from thinking it's empty (at least I still get no content when I open it).