Hi,
This bug is in our bug database and will be fixed shortly.
Several operations don't trigger the "Is modified" flag yet and the save function stays disabled: enabling and disabling nodes, but also component automatic update.
Also when you modify a parameter in the property window, the save function is enabled only when the modification is validated (i.e. when the selection changes), whereas it would be more convenient to enable it as soon as a first parameter is modified.
Thanks for reporting this issue.