It will be nice to have an option to lock specific file or directory from any modifications. (Probably, a button on the toolbar + a padlock icon in the status bar. I'm not sure here.)
When you apply "lock" to a file or directory:
* You can't modify it. (Of course, this is for files only.)
* You can't create new items in it. (Of course, this is for directories only.)
* You can't change its name, label, tags, comment, etc.
* You can't move or delete it.
For directories, it should work recursively. (When you apply "lock" to a directory, it is also applied to all files and directories inside it.)
Yes, there is file-system-level option to mark files as read-only. As you see, my idea is different.
We can call it "To protect" instead of "To lock".
In my particular case, locking/protecting of the directories (with an additional color label) is very useful for finished projects. (To avoid accidental changes as well as a guarding against over-perfectionism.)