Launchpad Entry: https://blueprints.launchpad.net/inkscape/+spec/extensions-presets
The goal is to add a drop-down list to the extension parameters list allowing users to choose a set of predefined parameters such as "default" (the parameters defined in the inx file), "last used" and presets defined by the author of the extension, but also presets saved by the user (unlimited number).
It could also be useful if we wish to reduce the number of predefined filters by grouping them by filter type.
The drop down list could be added at the bottom of the extension. A preset management dialog and a button to call it from the main extension dialog are also needed. The UI design could be very close to what is currently available in the Gimp.