If i accidentally delete text is there a way to "UNDO" that?

Hi there, there is no GrapheneOS notes app, so it sounds like you've installed a 3rd party app. As such, it depends on the app being used. Many notes app have "trash" to recover deleted notes, or undo buttons etc. It's entirely dependent on the app being used.

Also keyboard apps such as HeliBoard have undo/redo features.

You could also attach a USB or Bluetooth Keyboard to bress CTRL+Z