It would be great it every execute-command has a
brother which does not ask for variables if they are
already defined, e.g.
execute current:
ctrl-return: don't ask for variable if it already exist
shift-ctrl-return: always ask for variable
execute all
F8: don't ask for variable if it already exist
shift-F8: always ask for variable
execute next
F8: don't ask for variable if it already exist
shift-F8: always ask for variable