A useful feature I recently found in Maple is the ability to display the
input as formatted math like the output. Maple implements this
feature by only displaying the formatted input and output, and letting
you edit the input commands in a text box at the top of the window.
The feature seems like it would be useful in debugging input
commands. The easiest way to implement something like this in
Maxima would be adding a boolean variable %echo_input_formatted.
It defaults to falce, but when set to true, Maxima would simply print
the input as formatted text before it prints the output. It may even be
worth it to provide a function with the same effect for case by case
use. Something like echo() perhaps.