Sizo,
Threre are some circumstances where the editor doesn't recognize a change has been made to in turn enable the Save button. When this happens I frequently try this as a work around.
1) Try changing another field on the same property panel.
2) If the save enables, make your original change as well before saving
3) After saving change the other field back to it's original value and save again.
4) Navigate to another item so a different property panel displays
5) Navigate back to the original to confirm the change has been saved
I would also contact support and open an issue / ticket so this can get resolved in a future editor build.
--Bill