b64folder.fold: Call "Fold Base64 Code" to fold all occurrences.
b64folder.unfold: Call "Unfold Base64 Code" to unfold all occurrences.
On-save fold: Every time the file is saved, all occurrences are folded.
On-close unfold: When the file is closed, all occurrences are unfolded. ⚠ But not the case with closing the entire VS Code program, in which situation all folded occurrences are left with a placeholder and could not be recovered if you do not have an undo history.