variables used in the program and their names
This is something that both Stefan and Thorsten have been suggesting. They say that instead of all the registers being displayed in the right panel, the GUI could employ a parser/scanner/preprocessors, which goes through the code and extracts the variable names actually used in it; these are the ones which should be visible.
Furthermore, one could even give up then the restriction that variables need to be called x0, x1, x2... It could be whatever the user decides to call them.
It is not an urgent request, I'd say. We can keep it for consideration in future versions and discuss how desired/sensible/easy to implement it would be.