@ben has postet a workaround in Github.
The workaround, for now, can be set thru custom design, here’s an example:
… and after you set a property on @page level:
@page {
size: A4 landscape;
}
Supported values for this:
A5, A5, A3, B5, B4, JIS-B5, JIS-B4, letter, legal, ledger (and corresponding combinations with portrait/landscape).
You can see all values here: size - CSS: Cascading Style Sheets | MDN
Of course, you can always set page size with your custom values if provided presets don’t fit.
@page {
size: 4in 6in;
}