Anyone have a recommendation for the best way to repair a crack in a window? I know it won't fix the crack, but hoping to at least keep it from getting worse.

If it's single pane, google glass repair and have a "pro" replace the whole pane. Most windows are made to replace the panes relatively easily. My single pane window was $75 to replace the glass. Double pane will probably be more, but it was less than expected.

If you want to try something, since it's already broken and their isn't any harm, take a razor blade and scratch a line perpendicular to the crack and just in front of it. As the crack spreads, hopefully it will follow your scratch and head toward an edge instead of straight through the pane.