These options were present in earlier versions of OOo, and allowed the
appearance or basic widgets to be changed to suite the user's preferences.

They appear to have been lost when the native widget framework was partially
introduced. I have seen it said that the native widget framework makes these
options redundant, but that is not the case for two reasons:

The native widget framework does not work on all paltforms, therefore all of
these options are still needed on platforms not supporting the native widget
framework;

Thwe "Flat Buttons" option refers only to the toolbars, which do not use native
widgets even under the framework.

I therefore think that all of these options need to be re-introduced for
platforms not supporting native widgets, and the "Flat Buttons" option be
re-introduced on all platforms, until (if this ever happens) OOo uses native
widgets for all surfaces including toolbars, on all platforms on which OOo runs.