One option is to store files as a database like SQLite, which I assume is designed around not rewriting the whole file on every change. For example Audacity 3.x does this.
However SQLite stores multiple files on disk for crash persistence, complicating matters. But then again so does Audacity 2, and Microsoft Office to an extent (file locking rather than data integrity).
Microsoft Word used to only append changes to the document on save rather than rewriting the whole file, but this was disabled since if you deleted text and saved the file, it remained in the document. https://www.cnet.com/culture/microsoft-disabling-word-2003s-...
Modern file systems address all of that and more - without the added complexity of a whole freaking RDBMS system! If you are going to change an application it makes far more sense to just update it to leverage the features of a modern file system.
However SQLite stores multiple files on disk for crash persistence, complicating matters. But then again so does Audacity 2, and Microsoft Office to an extent (file locking rather than data integrity).
Microsoft Word used to only append changes to the document on save rather than rewriting the whole file, but this was disabled since if you deleted text and saved the file, it remained in the document. https://www.cnet.com/culture/microsoft-disabling-word-2003s-...