[knc1]

Changing the selection of font sizes IS that easy, use the:
FONT_RAMP
file in the top of visible USB storage.
(Search for that term here.)

But they did not do the same with the margin configuration.
Would be nice if they had, even as an undocumented feature as the FONT_RAMP feature is undocumented (by Amazon).

Posted on this forum is also a good solution to these sort of changes -
JBpatch
It modifies the *.jar files as the Java system loads them, rather than change them on disk.
But that tool has not been maintained and I was not able to get anyone interested in working on it when I last tried.
(I haven't written anything in Java for over twenty years, so even if I had the time .... )