I go to File / Templates / Manage Templates / Default / Edit.
The Page layout menu is grayed out under “Format / Page” so I give up.
Next I try to create a new Default.ott with my desired Page Margins and I overwrite
C:\Program Files\LibreOffice\share\template\common\styles\Default.ott
But to no avail, because when I then create a new document it does not respect
my custom margins from Default.ott
Is the world evil?