Currently you can only determine the default values of expression parameters. This is essentially a type of "preset" that is applied at initialization. It would be useful to allow users to create more than one such preset (with the default preset being special in the regard that it must exist and cannot be deleted I suppose) and allow the user to apply them in the client through the expressions menu. Ideally the user could even create and edit these presets in the client at runtime to save their favorite configurations of their avatar for quick access and edit ones that were created/provided by some other author. This is conceptually similar to the "Looks" feature and might overlap sufficiently to be integrated into one another somehow.