You're making sense, if you mean to request that transformations
of variables could be written into a model specification.
However, I would dispute that this is a "GUI" feature: it
requires typing the model specification. The gretl GUI model
dialog doesn't require (or allow) any typing of the model spec.
Yes this is not really a GUI feature but it is indirectly related with
the GUI as well. Currently, you run a regression and end up with a lot
of newly generated variables, which really don't have to be
permanently in the variable list. Again, this becomes a problem if you
have relatively big projects with a large number of variables. Running
a few regressions crowds out the whole variable list unneccessarily
sometimes. Of course, you can remove unwanted variables one by one
afterwards but still, this is a good feature request, which will also
promote a tidier design IMHO.