In Dungeons the Dragoning, each sword school provides an action type (generally only one) that can then be used as the basis of a maneuver. When grappling, if you are not in control of the grapple, the only thing you can do is try to escape or gain control. Maintaining control requires a full-round action. Successfully doing so allows one of a relatively short list of follow-up actions, none of which appear (so far as I can tell) to be unlocked as the basis for core rules sword school maneuvers. Successfully gaining control just yields the same set of available actions.
At the same time, the Setting Sun sword school has an optional (-2) drawback of "may only be used while grappling". It seems that this implies that it should be possible to use sword school maneuvers in some fashion while in a grapple. How can this be done?
Note that this question is specifically about the rules in the core books - Dungeons the Dragoning and For a Few Subtitles More. I'm not looking for solutions from homebrew.