The Save button in the top bar both saves your work and shows its current state.
Autosave
New templates have Autosave on, so your changes are saved automatically. The button shows Saving while it works, and Saved once everything is up to date.
Autosave is set per template. To turn it on or off, hover the Save button and choose Enable Autosave or Disable Autosave.
Saving manually
With Autosave off, the button shows Save. Click it to save your changes. It stays greyed out while there is nothing new to save.