Projects save themselves. There is no save button. The chip in the editor top bar tells you the current state, and it has four values.
Saved
Everything is stored on our servers.
Saving
A save is in flight. It fires about a second and a half after you stop making changes, and it is deliberately held while playback is running so it does not fight the preview.
Offline
A save did not reach us. Your work is still in this tab, so do not close it. Check your connection. It saves itself when the connection comes back.
Unsaved
There are changes that have not been sent yet. This normally turns into Saving within a couple of seconds.
What does not survive closing the tab
A file whose upload never finished. Until an upload lands, that clip exists only in the tab you are looking at. Reopen the project and it renders a slate reading ⚠ Media missing with the line about the upload never finishing. Everything else about the clip is intact, so re-importing the file puts it straight back.
Undo
Ctrl+Z undoes, Ctrl+Shift+Z redoes, and the clock icon in the top bar opens a History list you can jump back through by clicking a step. A whole AI run undoes as one step.
Undo lives in the browser and is lost on reload. There is no saved version history on the server, so you cannot roll a project back to yesterday.
Deleting a project
Permanent, and the confirm dialog says so. There is no trash and no restore. Your uploaded media is not deleted with the project, but any finished exports of that project are removed immediately.