tpt.setwindowsize
Changes the window settings. Scale is either 1 or 2. Scale defaults to 1, fullscreen defaults to off. Returns a number, 1 indicates success.
tpt.setwindowsize(number scale, toggle fullscreen)


https://powdertoy.co.uk/Wiki/W/Lua.html#tpt.setwindowsize

yes, it's an Lua command.

I wanna contribute D:

type this into console to make it a normal sized window:
tpt.setwindowsize(1)

and for double sized screen:

tpt.setwindowsize(2)

:D

Just delete powder def and pref etc then copy powder toy into your file and delete the origanal-stamps and saves still work and it takes just 1 min