This would be an amazing quality of life addition, making remixing filters together far easier.
Implementation: Modify Edit Rule page adding “Copy” and “Paste” (with overwrite confirm dialog for paste) buttons or icons in lower left.
All the functions to export and import XML to and from the clipboard should already be in the game, so this should be on the simple-ish side to implement. The Edit Rule window is what comes up when you add or edit a rule, so it’s one UI to modify.